Use Google Maps Places API and insert your customer's custom locations as given here.
Then you can request for a list of your custom places within certain radius and even sorted by how close they are to the current place using this simple http url
https://maps.googleapis.com/maps/api/place/nearbysearch/output?parameters
where paramerters would be radius in meters and optionally rankby distance if you want it sorted accorting to distance..That would return JSON with all your customer locations within that radius
Refer this to learn how to search
