There is an article on Rapido couplers in the May issue of Model Rail. It says the Peco uncoupler is simply an electromagnet and will only work with couplers that have no spring - also I believe they need to be fitted with an extra metal piece so the magnet can lift them. It also mentions mechanical uncouplers for the Rapido type from Fleischmann (9112), Roco and Minitrix, but there is no information on whether these can be fitted to Peco track.