I got my palm from radio shack, and exbal from perry online.
You put all but your current atmosperic conditions in before hand and it saves them, you still need a way to read current conditions, temp, humidity, bar pres and alt. in some form or another. its not diffacult once you play with them a bit.
here's a link to perry systems, the makers of exbal, they have a tutorial of sorts online http://www.perry-systems.com/