Instead of waving your hand to hail a cab, or even pulling out Uber to digitally summon a taxi, you call up a map that shows which cars parked along the sidewalk you could drive away right now. A few taps on your phone, a lock clicks open and you’re on your way.

Instant, ubiquitous mobility is the future as imagined by RelayRides, the Airbnb of car rentals. The San Francisco-based company just announced its acquisition of Wheelz, its main startup competitor, in a deal that puts new corporate and technological weight behind this vision.

Last year, Zipcar led a nearly $14 million investment round in Wheelz. Its acquisition now makes Zipcar a RelayRides shareholder, says Andre Haddad, RelayRides’ CEO. Zipcar itself was bought a few months ago by Avis. The Wheelz deal puts traditional car rentals in the same sandbox as idealistic peer-to-peer car-sharing, which suggests the mainstream industry sees the RelayRides concept as more than just a utopian fantasy.