Indeed.
The trouble with PDAs is that nobody makes them anymore; even if you get an old one off ebay, getting the power/data cables & connections sorted is a major pain.
As RBF points out, the fashionable thing to do these days is buy a car satnav with Win CE as it's operating system & change the settings so that it loads programs from an SD card. Have a look at this
Skydemon forum. It seems that you can get software to run on many cheap satnavs simply by changing the name of the yoursoftware.exe file to cheapsatnav.exe & then saving it to an SD card.
Once you've made it work with SkyDemon, you should be able to repeat the process & run gliding nav. software on it as well.
I'm sure that SkyDemon is compatible with gliding, it's just not as useful as dedicated gliding software. The best solution is a single device that runs multiple software (and a separate logger).