I saw a climber using a device I assumed was a GriGri while he belayed a lead climber. I noticed his hand was not on the brake rope. I reported this to the Duty Manager who went to chat to the climber. It turned out that the climber wasn't using a GriGri but a Camp Druid. The DM feedback to me was that the device had a trigger that was held by the left hand while the right hand payed out rope. The climber also came over to me to show me the device and he was really pleased with the way it operated. I told him I hadn't seen one before and that I was surprised such an innovative device hadn't had any marketing. I have since checked out the device on the Camp website and it is actually a descender and not a belay device - listed under the Rope Access pages. I've fed back to the wall and told them that this device is not a belay device but a descender. It's now up to them how they deal with it. Personally I feel this is a near miss although the device clearly works as a belay device as the climber held a fall while the DM was talking to him.
For what it's worth i've been climbing 40+ years, hold CWI, CWDI and IRATA.