I use a nice (free) process manager called ATMonitor for Mac OS X that has a lot of cool hidden features, one of which is being able to click on a running process and set the "renice" from +20 (less priority) to -20 (highest priority).
The best part is that it sticks between restarts. So you want XYZ to get full attention all the time, you set it once and it's done.
I want to do the same thing (renice a process) on an iPad running a particular daemon, and I don't know how to set a renice permanently.
I can do it once, and it works fine, but the setting is lost on a reboot. I read somewhere.
Now, as for permanently resetting the priority of a process, this can't be done directly. You can fake it, however, with a shell script that starts the app and then immediately renice's it. Give that script a ".command" extension and it will be double-clickable in the GUI. Not very elegant, but it gets the job done.
But as it says, not very elegant, and I dont think this is how ATMonitor does it.
I found this question and they gave a way to do it as a launch argument, but no apparent way to save it as a persistent value. For instance, if the program wasn't going to be started by launchd.
How do I set a permanent renice level, per executable binary, independent of its PID, when, how, or why it was launched?