Looking for a way to keep track of mobile phone. Any suggestions?

Family member recently diagnosed with Alzheimer's and frequently "loses" her mobile phone. Plans are to have her moved to AL hopefully soon. What has worked is for me to ring her number as she walks around house listening for it. That isn't working this time...could be out of battery or turned off. I use an iPhone (iOS) via AT&T and she has a Samsung through T-Mobile (Android?) but her plan has only talk and text. Is there some gadget that would enable me to "find" her missing phone from afar? If she were using an Apple-type phone, then I'd use the Find My Phone feature, but that does not work cross platforms. Ideas or suggestions appreciated.