Need to build a navigation app exactly like google map with own customized features.

I was planning to build an ios navigation app that will be on top of Google Map but should have some of my desired custom features inside. I need to add a radius feature that allows me to select certain neighborhoods of my city and I should be able to apply that radius around it. The radius should have features to spread in and out (I mean to increase or decrease the radius size) using miles as a distance unit. It should have the feature to add or remove a radius from the map. I need an alert feature too which sends me a notification with the message written in the alert feature whenever I enter such radius zone which I create.