Earlier quoted context omitted.
Tools for snooping in on your kid's spending is an instant ugh reaction from me.
I used to think so too, then I had kids :) One interesting approach is to use snooping tools but to then explicitly tell the kids and to discuss the results periodically. I.e., "my job as a parent is to help you figure out how to be a grown up. Part of that is managing money. I noticed you spent money on X and wanted to talk about it" I think for the 'cellphone based GPS-tracking' there was also an explicit rule that…
>"my job as a parent is to help you figure out how to be a grown up. Part of that is managing money. I noticed you spent money on X and wanted to talk about it"
This will teach children to spend like someone's watching. It's external motivation, and it's likely counterproductive IMO. Better, in my opinion, is to let them find out the natural consequences of spending money - that is, not having it for other purposes, or needing to do things to get more money.