This one looks like a toy but it really has a lot of depth. Listen to the given rhythm and tap it back as accurately as you can. It's not as easy as it looks! The sheep appear on the left if you tap late and on the right if early. A great rhythm and memory tool.
For me this is the best metronome out there. You can pretty much program it to play any time signature and it has the option to add accents, which can also be saved for further practice sessions. Simple and good.
Jazz 2 5 1's
Another simple but very useful app. Pre recorded ii v i's in every key both major and minor versions. It also has two speeds. Sadly the loops are the same in every key, but as a practice tool you can't complain.
Frankly I find this better than band in a box. As soon as I downloaded this I paid for the full version. Tons of styles, chord types, time signatures. It's got it all. The only down side is that it is no longer available for older phones.