It requires Bluetooth 4.0 LE, which is only in a few devices right now (But that number will grow). If your device doesn't support Bluetooth 4.0 LE, you're out of luck. Period. Buy a new phone if you want to use a Galaxy Gear.
Updated Friday, November 15th, 2013
Another XDA user has posted a very detailed and interesting walkthrough of the steps taken to get it to pair with his Nexus 5. It requires access to a Samsung phone compatible with the Gear, but it seems like a much better solution than the one above.
Not all of the steps he's taking seem necessary. Here's my version of the hack:
- Connect your Gear to a compatible Samsung phone.
- Pull the file
/data/data/com.samsung.android.app.watchmanager/shared_prefs from the Samsung phone and hold onto it for now.
- Enable ADB on the Gear.
Using ADB, modify the following file on the Gear:
/data/misc/bluedroid/bt_config.xml. Find the lines where you should insert your phone's data, replacing the Samsung phone data. Here's an example with a Nexus 5:
<N1 Tag="your n5 bt mac address">
<N1 Tag="Name" Type="string">Nexus 5</N1>
- Reboot the Gear.
- Pair the Gear with your non-compatible phone over Bluetooth normally.
- Sideload the Gear Manager application onto your phone.
- Remember when we pulled that file from the Samsung phone in step 2? Push that file to the same directory on your phone.
- Run Gear Manager. You're done!
The previous method is still listed below.
A thread on XDA Developers (Many thanks to Oleg, who posted this in his answer and deserves upvotes) has interesting news! The software needed has been identified, and the APK's have been extracted. According to one user (Our hero, Oleg), following the steps on the thread and using the files provided there allows you to pair the watch and unlock it with a Nexus 4. A basic description of the processis follows...
- Install all the Samsung APK's from this upload, provided by XDA User blazespinnaker.
- Install com.sec.android.fotaprovider from the same upload. (Maybe not necessary?)
- Run Gear Manager. If you have errors, close it and run it again(?).
- Pair Manually with your Galaxy Gear.
Note that this is still not a perfect solution. Some features may not be working. However, you should apparently be able to unlock and enable ADB!
I'll update this answer as more information becomes known.
But for the rest of your question (about ADB).
This article indicates that you can enable ADB mode on the Galaxy Gear itself, which is actually kind of exciting. The steps are simple. The article also has a helpful video!
- Swipe to "Settings"
- Scroll all the way down to "Gear Info"
- Enable "USB Debug"
If you're on Windows, you'll doubtlessly need the Samsung USB Drivers. But other than that, you should be pretty much set!