We are considering using Device for RTLS tracking, where the Device resource would represent the tag that is given to the person or thing being tracked.  There are (at least) three types of entities we'd need to be able to track: patients, practitioners, and assets.   I still need to figure out exactly how we'll want to handle assets in FHIR.  An asset could be something like a patient's belongings, or mobile infusion pumps, wheelchairs, etc.

My proposal is to change Device.patient to Device.subject, and allow references to Patient, Practitioner, and Person.  Once I figure out what resource could be used for patient belongings, we can add that too.

I think in this case Pracitioner should be the reference, rather than PracitionerRole, since you are tracking the actual person.

I don't think RelatedPerson makes sense, but I haven't thought about that very hard yet.