This app was mentioned in 2 comments, with an average of 1.50 upvotes
Have you searched AppStore for ESRI developed apps... Like Collector
This is for Android, but... https://play.google.com/store/apps/details?id=com.esri.arcgis.collector Try out Sample Maps to see if it's what you could adapt to.
Otherwise you could create a Google Maps API website with JavaScript and maybe Google Forms that when a new point/pin drop was set, a Data entry is made of a Google Form loaded with the GUID of the location. You might have to pay for commercial API usage I suspect.
You may want to look for a client/customer lead tracking app that has basic GPS/location capture rather than going to a GIS then backwards to form capture for a customer/lead tracking system