We've seen the Logisys Optical Finger Mouse, an ergonomic mouse that takes up no space except on your index finger, and is supposed to free you from moving your hand around unnecessarily as you switch from mouse operating to keyboard. The button is controlled with your thumb. I'm not sure how popular these are, but now usb.brando.com.hk, seller of all things USB, carries another finger mouse model, which appears to be a bit bigger than the Logisys model (and priced higher, at $38 - the Logisys model is just $19, and appears to be sold by usb.brando.com.hk also).

My question is: Will this exacerbate the Blackberry Thumb problem I already have and spread it to my index finger?

More on ergonomic mice:
New ergonomic mouse - Wow-Pen Joy
SmartNav hands-free mouse
Mouse-Pen
Like Crocs for your computer: The tall mouse
Glider Mouse