A vehicle-to-grid interface (or vehicle-to-home) would be killer. Even a small power inverter would make for a fantastic mobile power source, in a pinch.
Imagine a mobile Brammo trade show: a pair of 55" LCDs (200w), LED lighting (100w), a trio of demo laptops (80w), a loudspeaker setup (say 300w ave draw), and a rack of free-use cellphone / laptop chargers (say 100w ave draw). 800w ish peak draw, could be powered for a full working day by an empulse 10.0 on prominent display.
Then you walk next door to the Honda tent, where they have a rather loud gas generator chugging away in the back..