Scheduling Service Activity where site within X miles?

Hi all,

We need to incorporate a feature into CRM to allow users to search for available appointments based on their location (postcode) and the address of the Site. We would like to reduce the customisation as much as possible, but are aware that there will most likely be some (e.g. distance calculator API). Ideally, the user would type in their postcode and a certain mile radius and then a list of available service appointments at sites within that radius could be booked.

I am curious as to whether or not anyone has ever had a requirement such as this or where to begin? Perhaps an embedded HTML webpage/resource on a custom entity for the search and booking of appointments? Any tips or suggestions appreciated. This is on CRM on premise 2015 Update 0.2

Many thanks