My parents never really had an issue getting in touch with me, mainly because I picked up the phone and responded to texts like a good son. But your kids might be more like my younger sibling, making them damn near impossible to get hold of because they never pick up. If that's the case you might need 'Ignore No More'.
To get it working, all you need to do is make sure the app is installed on all the devices in question (including your own), and then a single tap will send your child's phone into lockdown. The only way for them to regain access to their precious phone is to call you.
For the moment this is Android only, which means if any of your kids are iPhone users you'll have to find a better way to make them do as they're told. Maybe confiscate their pocket money or something. [Ignore No More via Engadget]