The name of elitefts ones was "blast straps":
http://www.flexcart.com/members/eliteft ... 95&pid=916
I also happened to see an url with some homemade stuff which looked really simple. The actual url didn't worked longer but googles image cache hold the image.
Looked like a piece of rope pulled thru a piece of plastic tube, and then tied to some small ring. Probably works quite well to.
(As in 25 cm or so tube, pull rope thru it, get a metallic ring and tie both ends of rope to ring so you get a ring of the tube. Tie another rope to the ring and fasten it wherever.)
I wonder if I should go that route instead, maybe not as good but almost 100 $ cheaper over here. Dunno if it's safe enough to put your head down from but except that =P. Home made stuff is cooler since it's cheaper and show you don't have to spend a fortune on training equipment.
The later is kinda sad though because I do consider to get kettlebells, though I don't know if I can justify the cost vs sandbags or basketballs filled with sand and for maximal strength and growth they are probably not that good.