I back FindMyDevice. Simple setup, just give it permission (The necessary stuff works is easy to give permission on GrapheneOS) And give phone numbers for it to allow. I personally don't have a second phone so I just put in my family's phone number. and as simple as them texting "FMD Ring" and my phone started ringing. Same with "FMD Locate" Which gave a general (But not perfect) location. Very good app, only wish there was a UI on the other phones end.