I'm not concerned with tracking where my kids are with these, but tracking their shoes sounds kinda useful. Average daily conversation in my house:

"Where are you shoes?"
"I don't know?"
"You were just in the middle of putting them on!?!!"
"Yeah but... I can't find them now."
"How? You had them in your hands?!?"
"That was, um, before I got distracted."
"*sigh* Let's go try and find them."