Unfortunately the OS I'm connecting to does not contain nohup. It's a busybox linux on an embedded device.

You can implement nohup as a shell script. See src/nohup.sh in ftp://ftp.slackware.at/slackware-3.3/source/a/sh_utils/sh-utils-1.16.tar.gz and the resulting usr/bin/nohup in ftp://ftp.slackware.at/slackware-3.3/slakware/a8/sh_utils.tgz. Reduced to the bare minimum, you just need a shell that implements the trap and exec commands. Having nice is a nice extra, but it is not strictly required; and even cat and [ (test) are not needed if you make sure you always redirect STDOUT and STDERR when invoking the nohup script.

Alexander