1) Circle of 6
This is a very simple and useful app that allows you to add 6 of your closest friends, and send notifications to them if you are in need of help. With just a two-touch sequence, you can send all of the 6 friends an SMS saying that you need help, along with a map that automatically geo locates where you are. You can also send SMSs that indicate you need to receive a call to interrupt an uncomfortable situation, or to notify friends that you are fine at the moment. This can be a critical app in India, when people in danger can request help with minimal effort.
2) One Touch SOS
Platform: Android, Windows Phone, Java-enabled devices