Looking for off-street parking in a crowded city is right up there with having a root canal. Luckily, it’s also a subject that mobile apps like Park.It are hot to solve.

The new app is designed to do one simple thing — show you where to find legal spaces nearby. It crawls street sweeping timetables and info on residential zones, timed restrictions, meters and other data, so it can display key information when you’re out and about. About to get a ticket? Park.It will even issue an alert when that space becomes prohibited. 

That alone is very handy, but in the first pilot area — San Francisco — users will also be able to see open parking spots. Unlike apps that cover garages and lots, this implementation would show availability on the street, thanks to the city’s MTA. The transportation agency installed sensors in 5 percent of the city’s parking spaces, and in addition to using the data for its own mobile apps, it also makes the open-source sensor data available for other developers who want to feature the real-time information.

Five percent may not seem like much, but it actually represents thousands of spaces within the city, and 3,000 people have already signed up for the app. The developer isn’t stopping at just the Bay Area either. The company plans to launch in other parking-challenged areas like New York and Washington, DC. It will be interesting to see how these cities embrace it (or not), since they tend to pull in a lot of revenue from parking tickets. Then again, San Francisco has welcomed mobile parking apps, figuring that the revenues lost will be offset by more people finding and feeding meters.

The utility of this app is hard to deny, though hopefully the design will get refined as time goes on. Warning: It’s not much of a looker. But it does corral the extremely useful set of data. If you’re a driver in New York or DC, you’ll want to keep your eyes peeled for updates on this service. If you’re in San Francisco, you can snag the Park.It app for your iPhone or Android device. (BlackBerry coming soon.) Or download San Francisco’s SFPark app here (iOS / Android).