Think its possible to go from

1- ODB II -->
2- RS232 to USB -->
3- USB to tablet thru USB control in host mode (or would it be periphertal mode?)

USB to RS23 $20
Female to female USB adaptor - you should have one already - but if not about $5 on ebay.
ODB II $60 from scantool

Think its do-able? Could be brought in for under $90 and foregoing the bluetooth. Remember USB control was not around when carman was first rolled out.