I think this is a pretty cool idea, especially for patients suffering from conditions such as Dementia or Alzheimer's.
My girlfriend's grandmother is currently in the early to mid stages of Alzheimier's and is being cared for in a nursing home. The home have provided her with a toy doll, who she looks after every day. She loves the thing, it keeps her company and keeps her grounded by giving her something familiar that she can cradle and care for. She knows it's a toy, there's no confusion surrounding that. But, it's just the fact that she has something she can keep with her and look after that makes it so effective and keeps her calm and happy.
When I went to visit her to meet her for the first time, the first thing she did was introduce me to her doll, tell me her name and let hold her. Seeing the smile on her face as I brushed the doll's hair and dressed her for the day was a real privilege and brought my SO to tears.
Things like this may seem weird from the outside, or to people with no real experience of them. But they're so simple and so valuable and can go such a long way to being a genuine help to a lot of people.
Absolutely patients suffering from dementia have a lot to gain in regard to these new robotic pets. Beyond the reminders I would imagine it could be quite lonely and disorienting having dimentia and a familiar friend (even if it is a robot) is better than spending days alone aimlessly.