>I'm thinking about to develop some applications por handheld pcs.
> - Which language or tool is the best for this?

Depends on the handheld. For Pocket PC (PPC), use the Embedded Tools that allow you to write VB or VC++ apps for PPC. Click here for more. I'm not that familiar with the evil Palm platform. Evan Delay should come along with more info for that platform. There's also a Universal Thread handheld forum that you should look at.

> - Can I develop and test my application on my pc and then using it later on my handheld?

Yes, you can do this for PPC apps. I know there are emulators for Palm as well.

> - Does the same applications work for Palms OS and Windows CE

No, the two are not compatible.