TimerTools is a Windows Phone app that should take care of all your timer needs. The app includes three core timer tools; stopwatch, countdown timer and an interval timer. Everything is laid out nicely with TimerTools, taking advantage of the Modern UI of Windows Phone.
The stopwatch has a lap timer that will display the laps beneath the main time. The best and worst lap times will be displayed at the bottom of the screen.
The countdown timer has an alarm feature and your most common countdown times can be saved as favorites for easy access. Favorites can be pinned to your Start Screen for even easier access.
Interval timing includes settings for the countdown, interval duration, duration pause, and rounds. You can also create a custom interval timer with varying interval durations. Interval timers can also be flagged as favorites and pinned to the Start Screen.
TimerTools' settings allows you to disable your Windows Phone lock screen and turning on/off the vibration and audio alarms.
TimerTools is a nice, simple timer app for your Windows Phone. There is a free, ad-supported trial version that is almost fully functional. The trial lacks the ability to define favorite timers, Live Tile support and the ability to share your times via email. The full, ad-free version of TimerTools is currently running $.99 and you can find it all here at the Windows Phone Store.