Good old-fashioned tech
Your review: This Magnet Nail Sweep works just like the one I previously had that burned up in a fire. Drag it along the ground and you will hear a "tink" whenever a nail or other piece of ferrous metal attaches itself to the magnet. I much prefer this drag along model to those with wheels. On uneven ground it gets in the nooks and crannies better. My old model was identical to this one. It found hundreds of nails left over from a new roof install, and that was after the roofers said they picked up everything. It also found some very specialized screws I dropped that came out of a 64 Buick Rivera. No way was I going to be able to replace those very special screws. This magnet is a staple in my home. Wear gloves when wiping nails and metal chips from the magnet to avoid any cuts.
Pros: Already described