Eyes forward.
Radar behind.

Vehicle detection alerts for Hammerhead Karoo. Sound and visual alerts on your ride screen. Free and open-source.

Download APK View source →
100m50m20m
Clear
Road is clear
Alerts

Two channels.
Nothing missed.

Visual banners on your ride screen. Escalating sound patterns through the Karoo speaker. Each channel works independently so you choose what suits your ride.

Clear

Road is clear

Approaching

Within 100m

Warning

Within 50m

Critical

Within 20m

Safety-first

Quiet in traffic.
Loud when it matters.

Closing speed analysis detects fast-approaching vehicles and auto-escalates their threat level. Traffic density tracking suppresses minor alerts on busy roads. The result: silence in normal traffic, instant alerts when genuinely dangerous.

Night mode auto-extends thresholds by 33%. Critical alerts always fire — no suppression can block them.

Closing speed

Fast vehicle auto-escalated, holding vehicle suppressed

Traffic density

Busy road filtering with 30s rolling window

Speed gate

Suppress minor alerts below set speed

Night mode

Auto-detected, +33% thresholds

Smart cooldown

Per-level throttling, 3-12s

Clear chime

Confirms when road is clear again

Data fields

Three layouts. One glance.

Small, Medium, and Large widgets built with Jetpack Glance. Color-coded threat level, vehicle count, and distance at 1Hz refresh.

Compact

Vehicle count with threat color background. Minimal footprint for busy screens.

Standard

Count + nearest distance or status text. Best balance of info and space.

Full

Threat label, count, distance, and status message. Maximum situational awareness.

Setup

Riding in under a minute.

1
Install
Download APK from GitHub. Install via ADB or Hammerhead Companion.
2
Add field
Edit a ride profile on Karoo. Add eiRadar data field. Pick a layout.
3
Ride
Pair your radar in Karoo settings. Alerts fire automatically.
Compatibility

Any ANT+ radar.

Works with every ANT+ cycling radar paired through Karoo sensor settings. Karoo 2 and Karoo 3 supported.

Garmin Varia RTL515 Garmin Varia RTL516 Garmin Varia RVR315 Bryton Gardia R300L Magene L508
FAQ

Common questions

Which Karoo devices are supported?
Karoo 2 and Karoo 3 with firmware supporting the Karoo Extension SDK (1.538.2049 or later). Both devices are fully supported with identical functionality.
Which radars work with eiRadar?
Any ANT+ cycling radar that pairs through Karoo's sensor settings. This includes the Garmin Varia RTL515, RTL516, RVR315, Bryton Gardia R300L, Magene L508, and any future ANT+ radar. The app reads standard ANT+ radar data, so compatibility is built in.
Does it replace the built-in radar display?
No. eiRadar complements Karoo's built-in radar by adding configurable sound alerts and visual banners. You can use both simultaneously. Think of it as an upgrade layer that makes the radar data impossible to miss.
What makes eiRadar different from the built-in radar?
Karoo shows a small radar icon on your ride screen. eiRadar adds two alert channels you can hear and see: escalating sound patterns that get more urgent as vehicles approach, and full-screen color-coded banners. You also get configurable distance thresholds, smart cooldowns to prevent alert fatigue, a speed gate, automatic night mode, and intelligent traffic filtering that stays quiet on busy roads but immediately alerts when a vehicle is closing fast.
What is the speed gate?
The speed gate suppresses low-priority Approaching alerts when you're riding below a set speed (configurable: 3, 5, or 8 km/h). This prevents constant alerts at traffic lights or cafe stops. Warning and Critical alerts always fire regardless of speed, because a stopped cyclist is the most vulnerable target.
How does smart traffic filtering work?
eiRadar tracks closing speed from distance samples and traffic density over a 30-second window. Vehicles closing fast (≥36 km/h differential) are auto-escalated one threat level. Vehicles holding distance or receding are suppressed. On busy roads with sustained traffic, minor alerts go silent — but a fast-closing vehicle gets escalated to Warning or Critical, bypassing all suppression. No settings needed, fully automatic.
How does night mode work?
Night mode automatically activates based on your Karoo's ambient light sensor. It extends all alert distances by 33%, giving you more reaction time in low-visibility conditions. No configuration needed — it just works.
Can I customize the alert distances?
Yes. Each threat level has adjustable thresholds: Approaching (100–200m), Warning (30–70m), and Critical (10–30m). Tap values in settings to cycle through options. Night mode applies a 1.33x multiplier on top of your chosen distances.
What alert sounds are available?
Four sound profiles: Classic (escalating beeps), Subtle (softer tones for group rides), Urgent (aggressive alerts for high-traffic roads), and Bike Bell (natural bell sound). Each escalates in intensity from Approaching to Critical.
Does it drain the Karoo battery?
Impact is minimal. eiRadar reads data that Karoo is already receiving from the radar sensor — it doesn't power the radio or run GPS. The extension updates at 1Hz with lightweight processing. Most riders report no noticeable difference in battery life.
Can I use it with other Karoo extensions?
Yes. eiRadar runs as a standard Karoo extension and coexists with other extensions. Each extension operates independently.
Does it work with Garmin Edge or Wahoo?
No. eiRadar is built exclusively for Hammerhead Karoo using the Karoo Extension SDK. It cannot run on Garmin, Wahoo, or other cycling computers.
Does it require an internet connection?
No. eiRadar runs entirely on your Karoo with zero internet required. No cloud, no accounts, no phone pairing. Install it once and forget about connectivity.
Does it collect any data?
No. Everything runs locally on your Karoo. No telemetry, no analytics, no crash reports. Ride statistics (vehicle counts, alert counts) are stored only on your device and never transmitted anywhere.
How do I install it?
Download the APK from GitHub Releases, then install via ADB (adb install eiradar.apk) or Hammerhead Companion app. After installation, edit any ride profile on Karoo and add an eiRadar data field. That's it.
How do I update to a new version?
Download the latest APK from GitHub Releases and install it the same way. The new version replaces the old one. Your settings are preserved across updates.
What happens if the radar disconnects mid-ride?
eiRadar detects the connection loss and shows a "Connection Lost" status on your data field. When the radar reconnects, alerts resume automatically. No action needed on your part.
Does it support imperial units?
Yes. eiRadar follows your Karoo's unit preference. If your Karoo is set to imperial, distances show in feet. If metric, they show in meters.
Is eiRadar free?
Yes. Free, open-source, MIT licensed. No subscriptions, no ads, no in-app purchases, no "pro" tier. The full source code is on GitHub for anyone to audit, fork, or contribute to.

Ride safer today.

Free download. One-minute setup. No account required.

Download v1.0.7 View on GitHub →