I have a Digitech Jam man, and think it works well for what you seem to be looking for. It comes with 24 minutes of record time, but by upgrading your flash card, as I have, you can save up to about 6 hours of loops.
There are only two problems I have found with this unit, one is that you are limited to 100 loops, which is almost certainly more than enough.

the other is that there is no way to set tempo apart from tap tempo...so if you're playing with a drummer who plays to a click trck, and you want to use a loop, you have to be spot on with your tap and cant set the tempo to an exact tempo with a dial or anything.

There is a metronome on the pedal, and various time signitures...

it's great for jamming, but not ideal for live shows...but close