Are you talking about the CVT oil pump? Or have some manufacturers started doing doing this on the engine oil pump?

Edit:
Well i looked it up myself and it seems that newer cars, especially more expensive cars have addresed the wear issues by upgrading the crankshaft bearing, hardened internal components, upgraded altenator and a specific type of battery for this use. (No mention of electric oil pump motors for average cars)

You also need to replace the (more expensive) battery every 3-5 years, so the cost is still comong back to you. Higher quality upgraded components + the more expensive and often replaced battery will all end up back on your pocket, like i said the system probably isnt worth the cost of the fuel and emissions savings.

And if you have an older car with this function, then you also have the component wear issues, see the video i mentioned in the first comment: https://www.youtube.com/watch?v=qu8cJ2t_ja8&pp=ygUpYXV0byBzdG9wIHN0YXJ0IGVuZ2luZSB3ZWFyIHRlc3RlZCBnZXJtYW4%3D