sorry to burst your bubble but mit beat you to the punch...
MIT shock absorber increases fuel economy
Levant Power Corp is the new company
Levant Power Corp.
In their testing so far, the students found that in a 6-shock heavy truck, each shock absorber could generate up to an average of 1 kW on a standard road — enough power to completely displace the large alternator load in heavy trucks and military vehicles, and in some cases even run accessory devices such as hybrid trailer refrigeration units. the group, which also includes senior Zachary Jackowski and alumni Paul Abel '08, Ryan Bavetta '07 and Vladimir Tarasov '08, plans to have a final, fine-tuned version of the device ready this summer. Then they will start talking to potential big customers. For example, they have calculated that a company such as Wal-Mart could save $13 million a year in fuel costs by converting its fleet of trucks.(taken from the first link)
it sounds really promising,however idling will be an issue