No, pop-up reminders are only visible if you are in an active CARET Legal session. However, there are several other reminder options to ensure you know that the event is approaching, even if you are not close to your computer.
When you create a new event, you can also opt to have reminders sent via email or SMS (text message to the cell phone on file for your account). You can set multiple reminders to ensure your bases are covered in the office or on the go.