Check out iFreeTools Creator - an online database application builder, which I am building over Google App Engine.
iFreeTools Creator allows defining your own custom database by specifying the Entities (or "tables") and Attributes (or "fields" / "columns") and get started with using your online database in minutes.
Help Docs : http://help.creator.ifreetools.com
For your specific usecase, you will find the Authorization Profiles feature useful. Auth Profiles enables fine-grain access control up to field level. The following blog post gives an overview of the feature..
You may also find useful the Google Maps based geo-location feature, wherein attributes of Geo Point data-type can be defined to mark geographic locations and can further be used to search based on nearness to a given location (show me all chapters near xyz).
If you require assistance in using the app, you can use the feedback form in the app to get in touch with me.