XDA Developers: This site is about certain PDA-phones, made by a secretive firm called HTC in Taiwan. Their makers named them 'Wallaby', 'Himalaya' and 'Blue Angel', but almost nobody knows them by those names. The mobile provider O2 sells them under the brand-name 'XDA', and that's what we had in our hands first. They're also known as Qtek, MDA, SX-56 and many, many other names.