For a smartwatch that is supposed to be an extension of your smartphone and let you know of various notifications right on your wrist, the Galaxy Gear is surprisingly limited, with only text and email notifications showing the full text of the message. However, this is more a limitation of Samsung's notification service on the phone rather than the watch's, and to overcome this limitation, XDA forum member Sepiroth887 has released AllTheNotifications (ATN) Manager.
What ATN does is let you select which apps send a full notification to the Gear, so you can check out the entire content of a particular notification. It's as simple as it gets and works quite well in our own testing, though currently ATN Manager sends notifications to the watch even when we're using our Galaxy Note 3, which shouldn't happen; also, some apps don't work too well with ATN, though that will likely be fixed in future updates.
To use ATN Manager, you'll need Android 4.3 and a supported device, like the Galaxy Note 3, Note 10.1 – 2014 Edition, or the Galaxy S4, after which it's simply a matter of installing the app, launching it and then selecting the apps you want to get notifications for. Do not foget to give the app Notification acces in the security settings.
Hit the source link for the details, and make your Galaxy Gear much more useful than it currently is.