TrackDay for iPhone is a lap-timer designed by track day enthusiasts, catering specifically to riders and drivers who frequent the track. The app focuses on capturing GPS data to automatically calculate lap times for each session on the track. Users have the option to download tracks for a nominal fee or utilize an in-app purchase to have the app "learn" the track from their session data. With features like Track view for analyzing racelines and Dashboard view for real-time lap and sector times, TrackDay offers comprehensive insights for track enthusiasts.

TrackDay boasts a vast collection of over 270 track configurations worldwide, with ongoing additions based on user input. The app emphasizes user engagement by encouraging feedback to include desired tracks. It's important to note that continuous use of GPS in the background may impact device battery life significantly.