GPS based mobile app using google maps api perhaps

Dog Logger An app that allows you to view which dogs are currently in a dog park. Using GPS in phone to recognise when you are in your dog park and have your dog or dogs thumbnail pictures with dogs name appear over the map maybe in a list form. Google maps api? Or google places? App - First time opening - goto page to Select dog park from all registered dog parks in the database. If it is not registered allow the user to search for their park and save it into the datatbase. They can then select that park as their default dog park. Panel with list opens from simple header with list. Select dog park (from DB) becomes default and future app opens to this park. Add dog park. Allow user to define their dogpark and save it to DB. Add Dog (Register dog thumbnail, name, sex , age, breed or cross into DB?) My Dogs (Dogs registered to this phone) When the app is active it should recognise when the phone approaches the park and automatically places their dogs thumbnail and name in a list over the map. If you are not near the park you can see which dogs are currently visiting the park. Thumbnails must ONLY appear when they are in the park. We do not wish to track peoples movements unnecessarily. Touching a thumbnail could display all the dogs statistics from database. No personal info about user is need just their phone number or some other identifier. I'd like some ideas for a simple build for ios and android phones. This is being driven by a community group hoping to bring people together through dog ownership. If the app were to take off those who assisted with the build will get 1st option to further develop the app. Kind regards