TaiG has released an untethered jailbreak for iOS 8.3 – but Cydia Substrate isn’t yet working, meaning that many third-party add-ons won’t run. MS Tweaks likewise don’t work at present.
The release notes suggest that the jailbreak installation may take several attempts.
If jailbreak failed, turn off WIFI and try again. If failed again, please use TaiG Pro to restore and try to jailbreak again.
If you’re not yet running iOS 8.3, TaiG Pro allows you to perform the upgrade as part of the data backup process …
If you want to open up your watch as well as your phone, three well-known developers recently managed to hack the Apple Watch to run truly native apps on the device.
As always, jailbreaking is at your own risk and is something Apple frowns upon