You can incorporate detectors into anything into which you can isolate a transmitting and receiving coil connected to circuitry/software to manage the electromagnetic signals and look for variations to alert on. You would need a sophisticated technology to ground balance the detector on the fly since it’s pointed into the soil and you have a constant variations of height in a shoe (walking.) Even with today’s best units, the performance of a “shoe metal detector” would be horrible. The signals would be lost in the noise and depth would be pathetic.
Coverage is another reason not to do this. A regular detector is like coloring a sheet of paper with a wide marker, where this would be like using a very sharp pencil. Our footsteps only cover a tiny percentage of coverage (100 square centimeters, therefore 200 square centimeters for 2 feet) versus around 3x this for a basic detecting coil. Then, add in the swing, and you have more than 50x the coverage of the bottom of a foot (unless you plan to swing your foot back and forth, which would get exhausting – and only cover 1/5th the area of a normal detector’s swing!) [this was back of the napkin calculation, I welcome improvements on my results]
If the reasoning here is to be covert, I would ask why? Prohibited areas are prohibited for a reason, often because they are Archaeological sites and here, nighthawks, trespassers and looters are the scourge of the hobby detecting community.
Why would you go to so much trouble to create a poorly functioning solution like this unless you had a plan to be secretive? If you do, I hope you are arrested and forced to watch as the prosecution holds up your ridiculous metal detecting sandals as evidence in a court of law. Please someone send me a picture if this happens.
Not to assume this, I can see other reasons for this, such as landmine detection, but honestly you may not know you have a mine until you step on it.
Bad idea, just get a lightweight detector.