I have Bose QC35s and they can be simultaneously connected (not just paired) to two devices at the same time. They can be paired to more, and you can cycle through paired devices with a switch on the headphones or use the iPhone app to select which two devices you want connected.

I almost always have both my Macbook Pro an iPhone connected. The switch from listening to music from the laptop to the iPhone (such as when I leave the office and get on the bus) is seamless. Simply stop playing music on the laptop and start playing music on the phone. I highly recommend them.