This may sound gross to some...(idk why people are so sensitive but whatever) but the free + gadget free solution is just actually squat on the toliet seat.
There are so many things wrong with this idea that it's amazing that anybody would even think about recommending it. First, toilet seats are NOT designed to bear the weight of anybody standing on them. They have light duty plastic hinges to essentially keep them in the proper position on top of the rim, and were never intended to support the full weight of a human. Next, the actual seat is often built of a wood composite that is heavily coated with a thick paint. These things can break without warning. Finally, if you fall, after doing something this stupid, either on the seat, or with the seat up, while standing on the rim, you take a chance of breaking the bowl. Porcelain china DOES NOT break in a friendly manner. It can create shards that rival surgical tools in sharpness. We nearly lost an elderly neighbor when he was attempting to remove a toilet. He undid the nuts on the floor bolts and was trying to break the toilet free. As he smashed at it with a bare hand, it shattered. He damn near bled to death, since he shredded his wrist and forearm, and the only thing that saved him was a quick thinking EMT who called for a medivac chopper. The bathroom looked like somebody was trying to remove his arm with a chainsaw.
Finally, I have some regrettable experience with this being a common practice, and I know for a fact that it's horrifically unsanitary. I was supervising the electrical installation at a new hotel, and the framing contractor had found a new low in illegal hiring. He had located a whole crew of very small South Americans who were apparently from some indigenous mountain area. They didn't know a word of English or Spanish. As soon as they showed up, the portable toilets became a no-go zone. The seats and bench area on top of the storage tank of the units were literally sprayed with feces. After a bit of investigation it was determined that the little people were "squatters". Since it was a cultural difference that could not be bridged, I had to contract for separate toilets, that were kept a distance from the building, and locked, to keep them from being bombed. The National Park Service is having similar issues with some foreign visitors and now have signs in English, and other languages, and international "NO" graphics, discouraging squatters.