Is there a way to write a program that would detect when a switch is activated (the light turned on) and automatically turn it off in a designated amount of time?

 

Like:

 

If:

Light A is On

 

Then:

Wait 15 minutes

Set Light A Off

Here is one I use for a closet light.

 

I use the "Status" option so the light will go off after 10 minutes no matter how it was turned on. If you want it to only timeout when the physical switch is pressed you should use "Control" rather than "Status".

 

Also, I use "is not Off" rather than "On" in the event the light is turned on at a dimmed level (i.e. 40%).

 

If
       Status  'Closet' is not Off

Then
       Wait  10 minutes 
       Set 'Closet' Off

Else
  - No Actions - (To add one, press 'Action')

So I don't need to program the actual switch? How does the ISY know that the switch was turned on? Or does the ISY get notified every time a switch's status is changed?

ISY would see insteon traffic. However, part of the process with ISY is to add (link) devices to it. One sets the ISY into linking mode, then does the same for the device. This process identifies each device to the ISY.