a) I rarely use eBay, mostly Amazon
b) I have several Bluetooth OBD-II adapters, $20-$25 from Amazon
c) Android I agree, nothing for $5 beats Torque Pro
d) For Windows I use the same dongles with TouchScan (OBZwiz comes with a USB dongle but does not do BT).
e) for the professional AutoEnginuity is best but pricy.
For more than you ever wanted to know see here.

Is the a FAQ on what to look for when buying a Crossfire ?
Has anyone ever used the CD changer input for an Aux Input ?
YWTK.