HI there. Thank you for your suggestion. You should be able to give attorneys access to only the billing module, so they can enter their time and nothing else. Would this not work?
The transient task solution wouldn't really do much--just email the recipients once when the note is updated. Fast forward a month later, and nobody will remember that they received that email, and might miss whatever is important.
Your pop-up slap-to-the-face approach would be much more effective at getting a user's attention.
