Regarding the Nagios approach, you could have your program log errors to file, then use Nagios to monitor the file - possibly using the check_logs plugin

If you're concerned about your programs terminating unexpectedly, you could either:

• do some basic monitoring to see if the process is still running (for long-running processes), or
• log a 'program starting' message, then write a plugin to check for subsequent 'in progress' messages (or a corresponding 'program finishing' message) within a certain time period, and raise an alert if you've not heard anything.

That would be the stuff that's most applicable to your situation as I understand it - there are plugins for an awful lot of sysadmin-related tasks, so I guess your use of Nagios is going to be dictated by how much of the other functionality is going to be of use. If your sole use is going to be for monitoring your own code, installing and configuring Nagios is probably going to be overkill. Still, it's nice to have options, eh? ;-)