Peugeot did the first OEM available unit.
Peugeot to Debut Diesel Hybrid Crossover at Paris Auto Show | Automobile Box
As far as someone doing a homemade unit, I have a feeling it's been done, just have to dig it up. 
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Volvo WIA42 VED-12 / 335 hp / 1300 ft/lbs / 9 mpg
Big n' Boxy, Never met a Hill it Didn't Like
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