What are the location based alarm applications available for Android? I want to know what apps can sound an alarm depending on my location. 

Obviously it would be better if the battery consumption is low.

I'd be happy if the application is free but wouldn't mind paying if it's working properly with not much battery consumption. Also please post (if you can) only applications that you've used. 

UPDATE: Sorry guys, I should have been more clear. The alarm I am looking for is something where I can set an alarm when I am in the bus/train and make it sound the alarm and wake me up before my stop.
Llama. A laymans version of Tasker. It can do so much more but should suffice with minimal battery impact as it uses cell sites to identify rather than gps.