Ideally for rain using weather adjustments or a rain sensor can avoid the need to having to intervene.
Currently, if you port forward the HTTP port (default is 80) for the OpenSprinkler, you can access it outside of the home network by using the external IP (http://wimi.com). Having the app gives you complete control on your mobile device without having to use email or SMS. In the future, this will be possible without port forwarding.