They've been around for a while so skip this if you know already. It's kind of a stompbox in which you can load various pedals models (over 200?) from a virtual library via bluetooth. I have to play with a pedalboard/amp these days and this thing is pretty useful since I can change it into a different effect depending of the context or the band I play for. The majority of the youtubes video didn't really do it justice: bad recording, distortion clippage, hum/hiss and over the top tasteless modulation... I compared a few models of pedals with real ones I have (Xotic BB preamp, Sparkle Drive) and could make the xtomp sound pretty much identical, which was surprising. Can't comment much on the amp models but some of the drives are great. I got some great choruses and modulation (but I don't use that too much), useable basic delays and reverbs (that can be tap tempo-ed). There are EQs and other things as well and even a cabinet simulation which I'd use if I'm caught on a gig where they don't provide an amp.
I figured I'd post here after seeing the hundreds of posts about "pedal profiling" or "what type of OD/pedal should Kemper implement".