I'm using the BlueAnt S1 and it reconnects without any problems. Not sure if you're able to get it still but works great for me.
http://docs.blueantwireless.com/pdf/S1UserGuide(en).pdf
If you take your phone out of range of the BlueAnt S1 for more than 20 seconds (without turning the S1 off), and then come back into range the S1 will search for your phone and reconnect automatically.
It can take up to 10 seconds for the S1 to find your phone and reconnect.