This simple widget allows you to disable/enable SIP through a simple widget on your homescreen. The widget also allows you to select the default mode for outgoing calls (always use SIP, always use GSM, or ask each time).
You can find this Widget in Google Play store here:
https://play.google.com/store/apps/details?id=eu.siebeck.sipswitch
It is also available on fdroid.org
The source code of this project has been published under the GNU GENERAL PUBLIC LICENSE.
See COPYING.txt for the GNU GENERAL PUBLIC LICENSE