There is no perfect solution for this with the i730. I just upgraded to WM5 and the notification is a little better. You have to go into the notification settings and you can set missed calls and voicemails to beep, vibrate, both and/or put a message on the screen. If you set it to both and then find yourself needing to set the phone to vibrate you will still be notified. If you happen to miss the initial notification, however, you are still stuck looking at the balloon. The WM5 upgrade also fixes some of the other items that were a little annoying. It puts a battery indicator on the top of the screen. It also allows you to use Wifi and phone at the same time. I am sure there is other new and better stuff but I am only a couple weeks into it. In order to upload WM5 you first need to have activesync 4.1 or higher. Here is the verizon Link for the upgrade if you are interested. It gives you a pdf install and users manual with a link to the download.
http://support.vzw.com/pdf/User_Manual_i730_WM5_Upgr ... »Good luck.