In concept it appear to be somewhat similar to a wireless TENS unit such as the Aleve. A big difference is that it is a SMART unit in that you control with a smartphone APP and the APP will keep track of how you used the device, your sleep patterns etc. Like with most TENS units a typical session is 60-minutes long.
It works by trying to interfere with and block peripheral nerve pain signals before they get processed by the Central Nervous System (CNS). Since it is the CNS that, in the end, is responsible for generating all pain that you feel, IF you can stop the CNS getting pain signals from the peripheral nerves, you can, in theory, minimize the amount of pain generated by the CNS. By and large TENS units work — though they only alleviate pain for some periods of time. It is not a cure. At best a temporary respite from pain.
The Quell, like other TENS units, should work — at least to an extent. It is, however, about five times the cost of the Aleve and the crucial electrodes that you have to replace on a regular basis are expensive.
What I have not been able to determine as yet is whether a Quell really is more effective than say a Aleve — or whether it is all hype. Yes, the APP is unique for now — but the APP does not play any part in reducing chronic pain.