Some years ago I remember reading of a proposed hybrid van or light truck that was to be marketed to builders and other contractors.
The proposed vehicle was INTENDED to be used for power generation, not just transport.
Cant remember the full specs, but AFAIR it was able to supply many KW at 120 volt AC, for site lighting and power tools.
The engine was to be stopped or started automaticly as needed, with power being supplied from the battery when possible.

Dont know if this vehicle ever made it to production ?

Most, perhaps all, hybrid vehicles use a power inverter to drive the electric motor at variable speed and permit of a brushless AC motor being used.
It should be possible for this same inverter to produce power for other purposes when stopped. Probably not a DIY project though in view of the cost and complexity of these vehicles.