Who hasn't pondered: If only I could talk, instant message, and take pictures with one device? Well, if you have, now you can. Sony Ericsson's P800 PDA-cellphone combo has a built-in digital camera. RIM is getting into the combo act with the BlackBerry 5810. It looks like a regular BlackBerry but it's also a cellphone. Meanwhile, Audiovox's Thera adds fully functional PocketPC software to cellphone capabilities.