If you experienced failure to reply to SMS, you probably need this application to avoid having to delete the received SMS messages in order to successfully reply.
Android doesn't always use the correct Service Center number configured in your phone to deliver your SMS. Android can use erratic information included in the received SMS to override the Service Center number configured in your phone. That tends to systematically fail with certain carriers, especially when replying to foreign numbers or while travelling abroad.
This app should be launched once after installing it and then you can forget about it and everything will just work fine.
On the first launch it informs you if it had to adjust any SMS that could have been preventing you to reply to SMS. After the first launch you should already be able to successfully reply to SMS.
After the first launch the app runs automatically only during message reception and you don't need to manually launch it anymore.
The only way to disable it is to uninstall it.
All this app does is to clear the problematic information stored in the SMS database that could lead to an override of the Service Center number. It guarantees you that only the Service Center number configured in your phone will be used to send SMS. This sounds safer regardless if you ever had SMS delivery failures or not.
The problematic specification (that this app disables) is described in the Android source as "rule from TS 23.040 D.6".
This app is open source and released under the GPL version 2.
v1.1: Retry a few times if the SMS database is locked by another app.