Having to double tap the the screen to trigger a manual lap isn't practical and is prone to errors when it's raining or if you are wearing a jacket. If there is an app that's already got this feature please let me know, I've searched for one but no luck.
I use the button like in native apps for start/pause/save/discard. For lap, I use the right swipe, as is used for back, as most other devices use onBack() for a lap (those that don't have a separate lap button). Catching the double tap is an app can be a bit tricky.
