Canary email client for iOS adds Apple Watch app, first third-party mail client to support LTE without iPhone
There are very few apps on Apple Watch that work over LTE, and the ones that do can be very limited in functionality. Most notably, third-party email clients either don’t work without the iPhone or don’t offer a Watch app at all. The first-party Apple Mail app is an exception to this rule, but you’ll run into the “please view this email on iPhone” message pretty often.