I've looked at a few of the shake lights and wasn't impressed with them at all.
I did buy an LED kit from Wally-World for my mini-Mag light for a little over 5 bucks and am very pleased with the results, it's very bright and puts out a light kind of like a florescent light does. It has 3 LED bulbs and with the two AA batteries installed, I could turn it on and leave it burning for a month before the batteries ran down.