I too thought this was crazy and cool. I bought this about a year ago (in the UK), its no longer stocked, but from maplins.co.uk). It was an unfortunate upgrade for an also unfortunate mini ring track ball, it too is obsolete and once needed both hands to wield effectively.

The blackberry mini finger trackball has a elastic fabric ring on the underside (not shown in your picture) – it is essentially for the index or middle finger. The thumb controls the ball and buttons. Unlike the blackberry phone, OSes uses dragging and dropping that means you need two thumbs! Cleverly the button on the right of the ball is to un/lock the left click (directly below ball).

However more than a minute of use, turns really nasty because of the ridiculously small size of this device, my hand turns into a hideously painful claw. Whilst the other hand tries in to rip the cursed thing off.

Yep! Yah need two hands to use this!!!

never really liked those trackpads, as one cant really operate them with one hand…