Toy ideas to use up Lexi's spare energy!!

I am looking for a battery powered toy that can entertain/exercise my 4yr old kitty, Lexi. She has lots of energy at night, but us playing with her for 30+ minutes with her toy mice or feather fishing pole just does not tire her out. If she wants attention and we are busy she "bites" (does not break skin), just to let you know she's there and wants to play. We have tried the squirt bottle and such. But I finally realized, she isn't trying to be mean, she is just bored. Her 5 yr old sister, Jade, is a chubby couch potato kitty and just isn't fond of running and playing with her for more than 5 minutes.
I need to get Lexi a toy that will amuse her. Any ideas??

http://www.petsmart.com/product/inde...04841&lmdn=Cat
I just purchased this cat toy for my two cats. So far, so good.

:) Also get your babies some cat furniture for them to climb & play on.. You can get battery mouses & several diff things.. My cats just love the bigg wheel with the ball in it.. They chase the ball around the wheel furrever.. Yes your babies are so Adorable with Beauty..

Do you have a laser light? My cats love the laser light. You can just sit while you shine it around the room, up the walls and they run and run. :D

Also, my cats love this track ball toy, similar to the one K2QC suggested. I have one like she suggests and also like the one in this picture of Tink on her Cat of the Day page.

http://catoftheday.com/archive/2006/July/20.html

Hope this helps!