I was tinkering and discovered a service that allows the website to utilize push notifications on cell phones and tablets. It's an app called Pushover. All you have to do is install it on your device, set it up, and copy the user key it provides you into your user edit form on this site. After that, you will receive push notifications every time you receive a new private message. The app is free to try and costs $5 for life if you decide you like it.