Websites are complicated these days. Even when we work locally, we typically still need to make a bunch of calls to external, online applications, on any given page load. If you're ever without an internet connection, but still attempt to work (novel concept, right?), then you have experienced this frustration.
Andrew Norcross recently created a fun plugin, called Airplane Mode. Airplane Mode attempts to find and prevent external HTTP calls while you have Airplane Mode enabled.
This is a fun little plugin that I'm sure Andrew decided to build while he was on an airplane or maybe in a remote Florida swampland. But hey, for the next time you find you want this, you may as well grab it off Github so you can have it available for your local installs.
Airplane Mode doesn't cover every scenario, and if you have ideas of other things Airplane Mode can turn off for making local development easier, I'm sure Norcross would appreciate it.
I love that Norcross builds stuff like this to scratch an itch. But that's not all he builds. If you haven't seen his company's new-ish plugin, Design Palete Pro, you should check it out too. It puts the power of customizing Genesis themes into a site owner's hands, and they just got placed on the StudioPress marketplace as the first third party plugin there.