I'm having the exact same problem ever since updating to Watch OS 2, done at same time as updating to iOS 9 on my phone. Updates to 9.0.1 and 9.0.2 have made no difference. All native apps, i.e., those with complications -- in my case Dark Sky, iTranslate, Citymapper, Elevate, The Weather Channel crash on watch while trying to open. The only other I have which also does that is the Apple Store App! All other apps open/work fine, and all work fine on the phone itself. Had the problem with my iPhone 6 Plus and it continues now that I've upgraded to the 6S Plus.
Did all the steps everyone described here and nada. Only thing I didn't try was an erase of the 6S Plus and setting it up as new (although I did one full erase of the phone and restore from backup after the initial set up which also was a restore from prior phone backup -- first time I set up watch as new and the second time restored watch from backup -- neither solved the issue).
On Sunday I created a case with AppleCare frontline tech who agreed I did everything she'd advise, and she arranged a call back with a senior tech advisor. Had that call on Monday and he took a variety of info to pass on to Apple engineers, and arranged a call back Wednesday. He told me they didn't want to put me through another erase of the 6S Plus this time setting it up as new (yet) unless they were certain that was the only fix. Sent him a link to this thread for what it's worth (got the impression he didn't look at though). Had the call back yesterday -- he advised the engineers wanted me to connect the watch to the charger, confirm it was charging, unlock it, go into the music app on the watch, play a song from the watch and confirm the sound is coming out through the phone. After that, try the native/crashing apps again. If they still crash, restart the watch (not a hard reset) and repeat the steps. Did all of this -- music played as expected, yet same apps still crashed (both times), now faster than before!
Next step was the senior tech advisor had me sync the phone with iTunes and while connected he had me upload my phone's diagnostics' file to give to the engineers. Next call back set for tomorrow evening for a status update.
Bottom line, nothing working yet, but he seems committed to sticking with it until the case is closed. I wish I had more confidence it would be closed with success, but feeling frustrated and therefore skeptical at the moment. I trust there'll be some kind of positive solution eventually though, hopefully not too painful (enough pain already)!