Since you are using a 7520, I would suggest that you try NextMail.
I use NextMail on my (non-Blackberry) phone. I have the one-touch direct-connect button set to my NextMail "Notes" direct-connect number. When I want to make a note, set a reminder, etc, while I'm driving, I send myself a voice note using NextMail. When I get back to my PC, I retrieve and play my NextMail notes. It works great for me!
NextMail is also handy for sending voice emails to your contacts at times when you don't want to type an email on your Blackberry. I believe they have a free trial.