Have you looked into Smart Tag stuff?
Hey, yeah, I looked into it, but there are many applications for tech like this, I'd like to know how to make one myself. You can tag your dog, your bag, you can tag anything pretty much.
If you look into the same technology as the airport beacons, they have two signals both are transmitted at the same time at say, 0/360 as you change your angle from north, the separation increases. that way, you know the separation of recept of both signals, that then shows what radial you are on.
in your case, you spin until it lines up, then your transmitter is on that line.
The kids receiver/transmitter that received the two, then dinged you back with pulses of the time diference, you could know the round trip.
I don't think I need a system that sophisticated. A friend of mine told me to look into BLE for this, I've found there are BLE modules with integrated antennas. As far as I understand I'd need to hook it up to a controller and make the code for signal and i would have my transmitter. Then I would need some kind of BLE receiver, which is where I'm stuck conceptually atm...