Very expensive per watt, plus needs a thermal difference for source.
I got a little camp stove that uses Peltier device to charge USB stuff and runs a little fan (rocket stove). Works great for little things like that.
But I actually do live off grid, and there is not an application where thermogeneration is useful in the real world.
I would like to use a fresnel lens to heat a plate of metal on one side of peltier device, with other side immersed in a flow of water (stream or such) and see how much power it would make. But it would require solar tracking to work for longer than a few minutes each day. Never got around to trying it, because solar "PV" panels are just too reasonable option.