That's a fascinating thought, since obviously it is bidirectional + there's already the ability to send a small custom payload when an object is marked lost.
If I was Apple I'd be extremely cautious about opening that up, though. Not everyone would be excited about the idea of their data plans and bluetooth bandwidth being used up to enable a free texting plan for every kid within twenty meters.
Think of how that would play out at elementary schools, with hundreds of students piggy backing off a handful of teachers' iPhones.