I've seen a number of web developers out there mention they write entire web apps (front end and back end) using just their laptop and no external monitors.

The ability to do that is attractive to me, as it means you can quickly change your setting and still be productive.

Are there specific features (even 3rd party tools) that have helped you become really proficient at doing laptop-only development?

I feel like there should be some Mavis Beacon style training to help you get better at using just your laptop screen for development!