Unfortunately, none of the PDAs will run UAE (they are not powerful enough to emulate the CPU AND the Chipsets). You can get UAE for Windows (incl X Box), Unix/Linux, MacOS, BeOS, DOS and there is Aros.
For the A1 and AmigaOS 4, for it to get off the ground it needs *Software*, until the Full version of AOS is released and developers start working on it. I can`t see it get a larger market.
Having the greatest OS in the world, is useless w/o software to run on it. People won`t buy it... simple as that.