Tech blogger Raphael Rivera, Chris Walsh and Long Zheng have released an unlocker called ChevronWP7 for Windows Phone 7. It is the first one in this category and allows users to install any apps they want on their phone without a Marketplace developer account.
“Unlocking allows the sideloading of experimental applications that would otherwise can’t be published to the Marketplace, such as those which access private or native APIs”.
“We’ve taken the pain out of the process involved and put together a super simple executable that will allow anyone to unlock any WP7 device on the market using a USB cable and just a couple clicks.”
“This tool is completely safe and reversible for the phone. (The app even allows you to relock the phone.)”