Firstly the JML Handsfree Can Opener. You just pop it on top of the can, lining up the wheels with the edge and press the button. It is held in place by a magnet and it just does the job for you. It does open the can slightly differently to my usual can opener so the first time I used it I didn't realise it had actually worked. The only drawback is that it won't work if you don't line it up properly which can be very slightly tricky. As my eyesight is also poor (something I would imagine to be common among elderly people who might find also this helpful) I occasionally misjudge this, but it's really no huge deal as a second attempt does the job.
Secondly, the Culinare one-touch. Pop this on top of a jar and press the button and the bottom grippers grab the sides of the jar whilst the job grippers grab the lid and twist. Then 'pop', the lid is undone. Magic!
The tin-opener takes 4AA batteries and the jar opener takes 2. My pal kindly brought them with batteries already in and months of use later I haven't had to change them yet.
For anyone with hand/wrist injuries, pain or weakness I really do think these are a great help. I would imagine either would make a very welcome gift for an elderly relative.