Reply to iPhone Apps in a Set

I've been very curious about these new apps popping up with one shots, loops, and even robust production tools. It's incredible what they do in such a small package, and I was wondering which would suit me more in a set.

Currently, I'm working with a DJM 800. I noticed that I could connect my iPhone into one of the channels on my mixer via Aux to RCA cable. I work with a lot of EDM music and was wondering which one of these apps would help me expand. Something that I could use to create an 8 count loop would be nice. I really appreciate any advice and help!!