Luckily I haven't need it yet, but so far I can say that the pairing process on iOS or Android was smooth like butter. You can register creating an account or login via Google, Apple or Facebook. I bought one for me and the rest were for my wife, my mother-in-law and for my father. They had no problem understanding how it worked and how useful these devices are to carry on the wallet and find the purse or even a silent phone.
The only con I can mention is that I'd swear that I've selected 4 yellow Chipolos and received the mixed pack. Not a big deal, but had to say it.