I'm still not exactly sure why you would want to do it, but it is interesting none the less. The Bluestacks App Player allows most Android applications to be run on a PC running Windows.
While I cannot see a use case for this, the developers do allow third-party APK installation on their App Player, which will allow developers to install their own custom applications on the system for testing. It's not 100% supported yet, but it does make for a good alternative to Google's Android Emulator, which can sometimes be frustratingly slow when testing your applications on the PC.
Anyway, check out the review by Ars Technica in the source link, it makes for some good reading.