First create a stay open application from this script in the AppleScript Editor and add it to your Login Items in the Accounts pref panel:
on idle tell application "iTunes" try copy comment of current track to tehscript copy name of current playlist to tehlist if tehlist = "scripts" then if player state is playing then pause do shell script "osascript -e '" & tehscript & "'" end if end if end try end tell return 5 end idle
To add a script, modify the name of the sound file in Finder (so iTunes will add it a second time) and drag it into iTunes. Then type your script into TextEdit and copy it into the comments of your sound file in iTunes. You can then use the Remote app from your iOS device to connect to the shared music library on your Mac and select the track in the Scripts playlist.
Note there is no way (that I know of) to send anything to the scripts from your iPhone (other than simply executing them).
[crarko adds: I tested this, and it works as described. I uploaded the script and a sample sound file provided by the author here. This seems more of a curiosity to me but I'm sure some enterprising scripter will make use of it.]

