It's a good idea -- maid service can be commoditized, and particularly if you need a last-minute sort of thing, it seems smart. It's also notoriously difficult to find a good maid without playing the traditional "networking" game -- referrals, Craigslist, etc.
Personally, however, I see this only as a fill-in-the-gaps kind of service (which may be exactly what they're looking to provide). I have a regular maid who's been working at my place for 6+ years, charges a very reasonable rate ($25/hr), and most importantly, knows the apartment inside and out - exactly where to clean, how I like it, how to do the laundry, etc.
The biggest issue I see is the risk of extra-market activity. Whereas with Uber, car service is a true commodity, if Get Maid sends over a really terrific maid, there's a good chance that the buyer and maid are going to make a private arrangement for future work and cut Get Maid out of the deal. Which leads back to the ideal model being speed and "non-regular" usage.