Using mine right now to stream near-perfect audio from my laptop to my hi-fi wirelessly.
This is almost £15 cheaper than I could find it anywhere else.
Plugs in to any RCA or 3.5mm jack input, pairs with a phone or laptop which supports 'A2DP' and allows you to stream audio to a hi-fi, headphones or whatever via bluetooth. Has an internal battery and charges like a mobile phone, so highly portable and concealable if used at home.
I can vouch for the audio quality, this doesn't suffer from the same issues as FM modulators, its near perfect unless you really crank it up to silly levels.