A simple GPS based app that will record your lap times for you.
Start it up, tell it where the finish line and first corner are and it will work out your lap times. Ideal for a track day or even an afternoon karting.
Please be aware, the app can only be as accurate as your phones GPS, as this is what is used for your location. In my testing, it looks to be within 0.6 seconds of transponder timings per lap.
Adjust your finish line detection radius in settings for smaller tracks, such as karting. I used the app at Rye House and it successfully gave me my lap times and average speed.
On the map view, the colour changes based on your speed. The faster parts are red, down through orange to green and then grey.
Backup your day to your device and restore when you want to examine your track times. (All saves go to 'Lap Timer Buddy' folder on your internal storage.