I've developed an (awesome) mozilla-based custom web-browser running on Ubuntu 10.10 that needs to always be open (it is basically a "kiosk").
If it crashes, which is easy to do in a single-threaded web-browser like mine, I need it to start right back up (actually, a 10 or so second delay before restarting would be okay).
Application Monitor for Windows would be perfect if it wasn't for Windows. I haven't been able to find something, preferably with a GUI, that does this.
I usually develop for Windows based systems so Ubuntu is a bit foreign to me.