Looking for Occupancy sensor ideas

Good evening all!

As always, enjoy reading and learning from these posts. I was wondering if anyone knew of any sources (checked online-only see patent and sales information) or circuit designs for occupancy sensors.
I would like to use these in my home in a first step towards a "smart Home." In my research, I am running across some units that will turn on when entering a room, then turn off after (apprx) 5 minutes. I would like to design something that turns on (kitchen lights), then turns off after the area is left. If anyone can offer some direction or areas for these circuit designs, I would appreciate it. Thank you!

I'd used pyroelectric sensors.

Is the difference between what you have found and what you want, the 5 minute delayed turnoff? Most commercially available units turn on when they sense a person in the room, remain on as long as the person mooves around (at least once within the delay time...5 minutes?), and then turns off only after it senses no movement for the full delay time.

Ken