Locator for keys for Alzheimer patient

Aug 9, 2018
I currently have information overload! Between all the engineers I work with telling me about all sort of different products and reading different websites, I am totally confused.
My mother-in-law is what they call a functioning Alzheimer patient. She still lives at home but with help. She has started losing things - toothbrush, hairbrush (she is hiding things) - many items we can replace easily and with little worry. However, she loves working in her garden and walking and has started misplacing (hiding) her house key. We are looking for something that can be attached to her housekey (which we are now going to put on a lanyard so she can wear) that when/if she misplaces/hides it, we can just turn on our phones (iPhone for me, Android for hubby) and locate her keys. We don't need anything really sophisticated. I have seen everything from GPS fencing? to monthly charges to UGH!!! Any advice would be greatly appreciated.