Yale make one which is available from B & Q. Its around €70 and plugs into the phone line with a base unit which you can put say next to bed and a pendant for round neck. Range for pendant is about 50-100 metres from base unit I think. You can put in message and up to 3 numbers and that message is then relayed in turn to the numbers. If one doesnt answer it goes to next one. There's also an "open call" facility which lets you speak with the person ( only from the base unit not the pendant) for up to 2 mins. Got one for my dad & works fine. We had a false alarm when he pressed the pendant button without realising when trying to open a tupperware container & pressed it against himself( it's depressed in the pendant to avoid this really ) , but overall it's fine. Good security.
Just noticed it's also in Argos