Fat Gripz are ok, though, they really don't have the same kind of feel as a proper thick bb/db + for what they are, they cost a fortune!!! (I'm actually selling my FG's on Ebay right right now since I pretty much never use them & have just purchased a custom made Fat bar dumbell handle).
I personally, almost bought some OLY rings/TRX, though, I couldn't justify spending so much money on such a simple piece of equipment. Instead I opted to get some duplex webbing straps, since A) They cost only a fraction of the price & B) The weight capacity for non-training specific straps is HUUUUUUUUUGE!!!!!!!
The only big issue I suppose is the ease of adjustment <