Biometrics/Fingerprint readers for Palms & Treos?

From Andrew Davis at MobileOptimized. I just received my new IBM Thinkpad T42. It includes a biometric fingerprint scanner that can completely replace the normal CTRL-ALT-DEL routine. I must say that's it quite convenient. But as I used it more I started to realize what a nuisance it is to not have something like this on my Treo. I'm one of those very paranoid Treo users. Its locks anytime the screen is off and I must enter a password to do anything other than receive a phone call. But this can be quite frustrating at times. Many of my co-workers don't even bother. They're checking email and making calls so often that locking their device is a serious issue. Plus, its not like its foolproof. I decided to glance at a co-worker while he unlocked his device, then told him his password. Can we say security by obscurity? The more I started to enjoy the fingerprint scanner on my Thinkpad, the more frustrated I became with the locking mechanisms for my Treo and had to ask myself why we don't yet have a biometrics solution of some sort for mobile devices. Now, I'm not an electrical or hardware engineer, so perhaps there are size or power constraints that make these unfeasible for mobile devices. But on the other hand, I've seen available in USB sticks which are both small and draw very little power. Perhaps there's some other limiting factor? As I look at how I hold my Treo650, I see many places where a fingerprint reader could go:
1) over the top where the current IR port is (for a forefinger scan)
2) on the right-side nearest the Treo logo (for a thumb scan)
3) on the left side above the volume controls for a middle finger scan
4) if a future Treo gets rid of the stubby antenna, perhaps one could be places there.

However, I also recognize that these are convenient places for a right-handed person like myself (we all know that lefties have the advantage... after all, if the right side of the brain controls the left side of the body, then only left-handed people are in their right minds). But a good, neutral placement would be the center button of the 5-way. It could scan a thumb print from a right-handed or left-handed person. Plus, the default auto-lock of a Treo without a password is to simply press the middle button of the 5-way to unlock it. Looking again at my Thinkpad, I realize too that on my Thinkpad I have to swipe my finger across the reader. However I've seen USB thumb readers where you just place your thumb on it and don't have to draw it across the reading interface. I'm curious why we don't have biometric devices like thumb readers in our Palms and Treo's yet. I'm also curious if other readers would see the advantages of this... of being able to immediately unlock your device by just touching it (and, of course, still being able to use a password when your fingers are covered in Cheetos residue).