The plastic bag / bicycle pump pressureball.com device seems tedious beyond belief. 50 pumps, flaps, bit, clips, checking gauges.......no thank you.
I use the Tourna Tennis Ball saver which is just a hard plastic twist tube. I use 4 tubes in total and rotate 2 tubes (6 balls) at a time which the other 2 repressurise. Works pretty well: http://www.uniquesports.us/mm5/merch...gory_Code=RKAC
But at the end of the day, repressurising balls only really adds value if you're playing on non abrasive surfaces or doing alot of group coaching. Play on most hard courts or macadam surfaced courts and the felt gets chewed off in no time at all.