Like several of the reviewers below I find this app to be really useful beyond the "ring"; cross and interval training in particular. One feature that would make this app a more complete timer app is the ability to add multiple warnings for each round. For example, if I have a 5min round I would like to hear a warning when 1min, 20sec, 10sec, 5sec, etc is left in the round. For any sort of training, this type of scheme allows you to pace yourself without constantly checking your watch/timer.
iUser2 about Round Timer