You have already got nearly there.
http://gateway/sendevent/...
Will issue an event into the event distribution network.
The event source is the remains or the URI.
http://sendevent/switch/my/lights
would send an event with an event source of switch/my/lights
The event type in this case would be http://id.webbrick.co.uk/events/uri
If you add a parameter of type to the uri then you can override the event type.
i.e.
http://gateway/sendevent/switch/my/lights?type=my/type
Any other parameters on the URI are added to the event payload
http://gateway/sendevent/switch/my/lights?type=my/type&lifier=lounge
Would send event with
eventtype= my/type
eventsource=switch/my/lights
payload { amplifer=lounge }
So anything that is capable of issuing an http request on significant data can be integrated with the gateway.
If you look in the sample page templates for one called HomeInt.kid you will see sendevent being used to do the home away states.