You can use voice input such as Amazon Echo or Google Home Assistant with OpenSprinkler. This is done through an integration with IFTTT. The basic steps are:

• Go to the IFTTT website or use the IFTTT mobile app to log in.
• Create an applet where the trigger (this) can be Amazon Alexa, or Google Assistant, or SMS text message etc.
• The action (that) should be a Webhook that sends a web request to your OpenSprinkler to trigger a certain action, such as turning on a zone, or start a program (to find out the specific HTTP command you need to use, check the OpenSprinkler API documentation). The web request method is GET, content type is text/plain.
• If your controller runs firmware 2.1.9 or prior, the web request requires you to set up port forwarding on your router, in order for an external web request to reach your OpenSprinkler. The port forwarded request is in the form of http://external_ip:external_port/command_and_parameters. For example, the request to turn on zone 1 for 10 minutes is:
  http://external_ip:external_port/cm?pw=your_password_in_md5&sid=0&en=1&t=600
• If you have firmware 2.2.0 or later, you can enable OTC token, so that you can send a web request using the OTC token without needing port forwarding on your router. The OTC web request is in the form of https://cloud.openthings.io/forward/v1/your_otc_token/command_and_parameters. For example, the request to turn on zone 1 for 10 minutes is:
  https://cloud.openthings.io/forward/v1/your_otc_token/cm?pw=your_password_in_md5&sid=0&en=1&t=600

Archived information: the content of the previous version of this article is in this blog post.