And yes, I can confirm this. I just tested a Logitech Bluetooth Headset along with the Griffin Powermate. No Problem indeed.
It's even more unlikely that this might have caused an issue as the Headset uses Bluetooth whereas the Griffin uses Bluetooth LE. Technically Bluetooth and Bluetooth LE have not much in common other than the name.
But also to use more than one Bluetooth LE device should not cause any issue (I just also tried the iPad Pro Pen which also uses Bluetooth LE) because Bluetooth LE uses a very lightweight protocol, low priority and low bandwidth so it is ideal for such kind of communication.