Laymens terms
do you have the ability to afix a motion sensor, security light and connect a cable to make it work ??
If so then buy a cheap motion sensor from toolstation, 30w security light from toolstation, cable and a 3pin plug, dependant on your install location you may need ducting for the external cable or armoured cable or grey or white cable, only you can decide
If this is not something you can do then you will need an electrician but they really are easily done by a DIYer, if you are looking for a battery powered sensor that just sticks to a wall and it works, nothing exists, you have to find what suits you best and work at a solution
When it is all wired up and working, the app will see that power is being drawn on motion, send a zwave signal to any switch or Smartthings connected device and turn it on and off if needed
Even if your LIFX lights are wifi you can still use IFTTT to contrl them from within smartthings
I also have a proper security camera fitted outside that has awsome Night vision but you cant beat actual daylight for recognition, so it auto switches to daylight mode if the security light comes on add to that a Fibaro RGBW led light set up as well which switches to police mode on motion after a set time of night and all triggered by a cheap motion sensor, once you have the motion sensor installed you can have all sorts of fun
https://www.toolstation.com/shop/Lighting/d220/PIR+%26+Photocell/sd3296
https://www.toolstation.com/shop/p71754
or an all in one unit
https://www.toolstation.com/shop/p86366
app to make it work from the very awsome Cobra