"You have to understand, anything wireless is exposed to the ""air"" of network sniffers and hacking in a much easier format. It poses a security risk. It is one thing to put your computer that is hopefully well protected on the internet, but you are usually pretty well protected behind the router. With a wireless HDD broadcasting itself would only entice someone to fiddle with it. Even if the broadcasting is disabled, wardriving can easily pickup such devices.
I'd agree with the previous post, to buy a USB drive from Western Digital and share it. Your other two computers can access it via a network connection.
Of, you'd have to have your computers networked for them to find your computer that is sharing the drive. Then there are also the mini NAS drives (Network Area Storage), if you don't want to use USB but rather ethernet."