I have the sj4000 (watch out for fakes ones). Really good and fits gopro adaptors etc
I am looking at this one, it looks genuine to me.
http://www.ebay.co.uk/itm/161387517335?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT
Get the SJ5000X elite its on par with the hero 4 and light years better than the SJ4000
https://www.youtube.com/watch?v=EiXVm4I5ULY
The Hero 4 beats it at sound but there is a new firmware out to fix this and the go pro is 3 times the cost.