Nimbus is the new open-source project from Jeff Verkoey (who brought you Three20) that is trying to minimize Three20's sprawling, lengthy build process while providing extensive documentation and feature parity. There's an awesome launcher demo available as part of the project. I don't know about bindings or MonoTouch, but it's a very nice and elegant way to present a launcher. Try it out if possible.
Once you've used Nimbus, the only reason to go back to Three20 is for a feature it doesn't yet support. It's incredibly fast to build and use in general. I highly recommend it. It's also being extensively developed, so that's a drawback if the launcher is one such item.
The link is https://github.com/jverkoey/nimbus. Hope this helped!