Best way to add outside light with PIR to SmartThings?

I have an outside light with a switched supply and a PIR and I have wired an override switch in parallel with the PIR. The supply switch is permanently set to on and the override is usually off.

Can anyone give any advice for the following

  1. How to use SmartThings to override so that I can turn on the light and keep it on by remote control?
  2. How to detect that the light is on such as by the PIR and then make a short audible warning tone to warn of anyone approaching the house?

For my garage light I have had good results with the ST Motion Sensor and the Aeon Labs Micro Smart Energy Switch (DSC18103-ZWUS). I might try using a DSC18103-ZWUS with the load outputs in parallel with the override switch which I can then control using my mobile phone.

My SmartThings are not very reliable so all my installations must still provide basic operation independently of the hub.