No Longer in distance sense

[colc]

I'm looking to have built multiple devices that can sense each other if one of the sensors is outside a range distance a visual alarm is given ...I have no electronics background and would need some external help to get this built can any one advise...

 

[Externet]

Common device used to keep children within reach distance; typical brand is 'Guardian Angel'

Same for luggage :

----> https://duckduckgo.com/?q=luggage+distance+alarm&t=canonical

 

[colc]

hmm they seem to be very similar to what i need ...its a good starting point thank you