Can I turn my external USB HDD into a wireless HDD?
What you're looking for is a wireless USB hub such as this one (disclaimer: I've never used one, that's just the first Google result I found).
On one end, it has USB ports as with any USB hub; on the other end, it has a Wi-Fi radio that talks to your wireless network and exposes attached storage devices. For stuff like USB microscopes, oscilloscopes, &c., I wouldn't expect it to work, but something simple like a hard disk should be fine.
just found this: iUSBport . Looks very compact and versatile. Sells for the same price as the previous suggest solution. Hope it helps.