Heck, wouldn't even need that. sha-256 is a simple enough algorithm to do in hardware. The FPGA miners do about 100 Mhash/sec on 4.4 watts -- if this was a long term thing as opposed to a short fad it'd be very lucrative to produce an estimated $30 BoM dedicated card to output 400-500 Mhash/sec on < 30 watts (PCI, PCIe, single slot, works off of one molex). Something like that could easily sell for $300.
You could even have a dedicated black box device with a rudimentary CPU, embedded OS and a few megabytes of ram pumping out a gigahash or two on a 250 watt PSU. They'd fly off the shelves at $1000 (estimated BoM: $150).
The fact that we all think this is a very short term flash in the pan is exactly why you don't see cards/devices like that already.
You could even have a dedicated black box device with a rudimentary CPU, embedded OS and a few megabytes of ram pumping out a gigahash or two on a 250 watt PSU. They'd fly off the shelves at $1000 (estimated BoM: $150).
The fact that we all think this is a very short term flash in the pan is exactly why you don't see cards/devices like that already.