Call blocker for Android and/or WinMobile

Hello, We are looking for a vendor that can develop a simple application, proof of concept, able to block incoming phone calls from a phone number that's configurable on a settings tab. The application should intercept an incoming call before a standard phone application, hangup the call and make it unnoticed by the standard phone application if the caller number is that configured for blocking. Otherwise, when a call comes from different number, the application should allow standard OS phone system to process the call. Ideally we are looking for bidder who can develop the applications for both Android and Windows Mobile platforms, but will also consider options of only one platform development. Source code vendor will provide needs to be good quality and should be well commented, allowing our in-house developers to use it for our mobile products in the future. We do not care about application appearance at the moment, so vendor can use standard OS controls. When placing a bid, please list OS version numbers you'll be able to cover. Thanks, Max