Free Roller Derby penalty timer (WFTDA 2014 rules) designed to be simple to learn and operate. Clean, simple, ad-free interface lets you focus on NSO duties instead of the app.
Implements WFTDA rule 6.4.1 (two jammers serving penalties).
Long-press a timer to reset it to 0:00. Tap a timer twice to add a full minute (2013 rules).
You may download and modify the source code at no cost: http://woozle.org/neale/g.cgi/ptimer/