Another Ebay deal where the sum of the parts seems like a pretty good value. Must trigger at an adjustable DC level of reflected IR since the 4093 IC is just NAND gates, so this isn't a high tech sensor. A 38 kHz sensor & circuit would be more reliable, but who am I to look a gift horse in the mouth.
If nothing else, it looks like a nice PCB, so soldering the non-SMT parts may be fun for us old Heathkit lovers, or an intro to electronics for someone's budding young scientist. Win the whole science fair when your kid turns on a lamp or something else when you or Rover is detected.