3 ms·

Alternatively, just sell matching pairs of electronic tags (sticky) that both have buttons and beep when the other one is pressed.

• cubicle67 17y ago
  Yep. I'd be sticking them on my kids shoes
  • lacker 17y ago
    My girlfriend says she would stick them on her shoes too, and that's a lot of shoes.
  • wlievens 17y ago
    So that they go beep-beep-beep when they walk? That's cruel.