My almost 5 year old can't keep track of hers but my 9yr old hasn't lost it once, because she uses it for everything. When it's not for work it's for play.

Similarly my best friend tells me that her DH used to put his phone through the washer or loose it almost monthly and never answered it because it was never handy. Since getting an iPhone though he always has it and answers it, and has had it two years without washing it or loosing it. He uses it to photograph things he has to remember, for the calendar, as a timer, etc. If you get the right device perhaps it won't be lost? Or maybe not....