There is a lot to like about 3rings and I have no reservations in recommending it as a simple but effective monitor to check that a normally active loved one is up and about. It requires no special infrastructure, works very well for loved ones and carers and is a very cost-effective safety net for anyone living alone.
http://www.smartageing.co.uk/uncategorized/are-3rings-enough-to-know-if-mum-is-ok/
Smart Ageing