The advanced metronome is seriously the best I've ever seen, and believe me I've seen a lot...
The only thing I've wanted for awhile now in a metronome is the ability to program in the measures. For example, some music while practicing might have a measure of 3 where the rest are in 4. If there could be a way to have multiple beat patterns, and then control which pattern each iteration of the measure plays, that would be uber-helpful.