For Bangalore, Find My Ghar which is designed to provide real estate information. Anybody can post a property for the purpose of sales and then Google maps will show the location. To get more info, click on tag will open up a windows about property details information. Even you can make comments too.
Alerting system awesome and easily with the use of Google Maps you can search for a new properties and get your desired information.
Indian Google Maps Mashup Roundup! [via maps mania]