What exactly is the problem Mark?
Patients not bringing kit back in?

Why do they need to "trace the location" of equipment? Surely it gets signed out to a named person (or nurse) ... as well as a return date (date that it has to be brought back in by, or re-prescribed)?
And ... who prescribes the kit in the first place? Don't they bear some sort of responsibility here?
So ... if the kit doesn't come back ... just send out a *bill!

No need to be thinking about "high tech" solutions - a "low tech" log book will suffice!
@Bill - proforma invoice, if you prefer.