Lol. Forgot I had an account. Touchstone modder here.
First, see this post from a while ago on a test I did. Yes it is possible to use the touchstone (on most usb devices). If Govnah gives the correct readings, it should give about 500mAh of current (phone use, even standby will lower this amount. Consider it will get 500mAh if the phone is off). I will review this number when I get home... don't have a touchstone on hand. On vacation for one more week : ). Please copy the link.
Easiest way - if powermat releases a back door for the photon, rip out their internals and replace them with the touchstones.
Second easiest way - steal a right angle USB connector from the EVO or similar powermat back and wire it to the touchstone sticker. I don't own a powermat, but the angle connector simply looks to be the lowest profile micro USB connector. Put a case around your phone and hide the touchstone sticker in there.
PLEASE NOTE - if I remember the pre touchstone sticker and the pixi touchstone sticker have different +/- orientation. Be sure to test first
Hard way, historically done on the EVO 4g and other phones - solder the touchstone sticker to the internals of the phone.
When I say the touchstone sticker, I an referring to the sticker, coil and magnet combo removed from the palm case.
I have a herd of touchstone pucks at home. And in my car. I will absolutely get this working with no internal modification. It might require a $30 case just to steal the USB connector, but that option is up to you.
Why would you want to go through all the trouble if you don't own them already? The touchstone pucks are STILL $5 at verizon's web store... you could put them EVERYWHERE!!!! : D