When used correctly in the right places - that is nowhere that would give an obvious false reading - the REM ONE works very well!
I have two of them along with a KII Meter. The other night, I used one with the KII. I would have KII spikes up to the third and fourth light and then the REM ONE would also go off. When I was recording this activity in IR night mode, just seconds after both devices went off, my camera (which was fixed) was nudged by an unseen force. You can hear the tap noise on the camera and see it shift its position significantly. Having the REM POD, in conjunction with other devices like the KII, being activated moments before a bona fide poltergeist moment shows that these devices work really well to reveal the presence of spirit activity.
Based on my experiences, I highly recommend the Para4ce REM ONE. It maybe the most basic and affordable REM POD, but it still does an outstanding job no matter your budget!
