Just been reading about an App for smartphones that alerts you if a child goes missing...some may already have heard about it.....similar to the Amber Alert System they have in the US I've no affiliation to the organisation, but if you're interested to see what it's all about then have a look at their site... could make all the difference... www.childrescuealert.org.uk
I imagine they'll be reconfiguring the software to make it available to most phones, tablets etc....I know they have pics on the milk cartons in the States...have done for years....
