YAMapKit based on Google Maps Javascript API.
Inspired by MacMapKit.
You can use Google Maps on iOS 6 just link this library in your application. YAMapKit is compatible with MapKit.framework.
YAMapKit implements nearly 100% of MK* functionality. It's been tested on iOS 5 and 6.
Unsupported Features
There's currently a framework and a small demo application.
Because the framework is API compatible with Apple's, you can use their documentation as a reference.
MacMapKit
https://github.com/Oomph/MacMapKit
MacMapKit is distributed under the BSD license. However, MacMapKit uses Google services to provide map data. Use of specific classes of this framework (and their associated interfaces) binds you to the Google Maps/Google Earth API terms of service. You can find these terms of service at http://code.google.com/apis/maps/terms.html.
YAMapKit is available under the MIT license. See the LICENSE file for more info.