I would be highly suspect. Stepping DC voltage up is not a simple task...only way I know of would be to convert to AC run through a transformer then a rectifier to convert back to DC. If this comes with a 12v power supply with a USB header I would not even allow it in my house, at some point someone will plug a phone into it and fry it.
The power inverter for the car also specifically puts 5v and 500ma (2.5 watts which is waaay less than the 18 watts the tablet is designed to draw at max).
Most USB ports are 500 ma....some are 1 amp but still less than 33% what the a500 needs.
I'd be very suspicious of this.
Sent from my A500 using XDA