I was just browsing my old Zaurus feed from the old days and I came across Nautik. It was a shareware app for solving most of the problems that sailor might have that could be solved with a handheld computer, this was the free version so there was no saving solutions, live use only. You could plot radar, celestial navigation, and other common nautical nav problems. The files are in a Zaurus .ipk file. Basically a Linux Zaurus .ipk file is just a .deb so rename it to XXX.tar.gz and open it with an unzipping program. Follow the directory path into data.tar.gz and you will dive into the file directories, the actual java files are in the java directory where the actual html and .jar file.
The java app is in German but can be translated, I used it as is on my Zaurus.
Abandonware it appears to be as the server no longer gets the Nautik webpage and emails bounce. It was offered in windows, mac, linux, Sharp Zaurus, and Ipaq formats. It is already optimized for handheld use so if anyone wants to make it useful again...
https://personaltelco.net/~dave/ipk/...java-0.7.1.ipk