As RadioShack apparently prepares to launch its own contract-free mobile service in early September, an anonymous source has tipped Engadget on the prices it will be offering. According to a leaked document, RadioShack No Contract Wireless will offer smartphone plans starting at $50 a month. Users will get unlimited minutes and text messages within the US, with 1GB of included 3G data. For $60 a month, the data limit is pushed up to 2.5GB a month, with tethering capability and visual voicemail added. After subscribers reach their cap, data is throttled, but more can be bought at $1 per 50MB. Both plans come with Muve Music, something that's also available through Cricket, which seems to be providing the infrastructure for RadioShack's service.

On the feature phone side, the slides show two tiers offering 300 and 1,000 minutes with unlimited messaging, just like Cricket. The plans cost $25 and $35 respectively — once again, those are the prices you'd get from Cricket. While the feature phone plans are pretty much the same, the smartphone tiers differ a little. Cricket smartphones generally work on a $55 monthly plan, which offers 1,000 US minutes with unlimited texting, Muve access, and 2GB of included 3G data. That means on RadioShack, you can pay slightly less for a lower data cap, and on either leaked plan, you'll get unlimited voice. The service is rumored to launch on September 5th, so all should be revealed soon.