I wonder how much a used UPS truck costs? Couple that with a 3 year investment plan for the system, and after that it's gravy.
Don't forget, that application could probably work for a USPS truck too, though you would be "inventing" it for yourself since as far as I know it has only been designed and applied to the UPS truck fleet so far.
Out of curiosity, what do you deliver? IIRC, business mileage (IIRC, even when you work for a business in case you do not own a business) is deductible at the Federal level, which IIRC is 40 plus cents a gallon. That's not chump change.