I don't think a wrist device would help.

As the great Yogi Berra once said, "50% of this game is 90% mental."

There are physical/mental devices, ways to think of what you're doing, but you have to do it. The basic idea behind turning the ball early is your body's subconscious or unconscious lack of faith in your ability to make the ball hook. So your body tries to help it. I do it also, so it's not like I'm talking down to you. You have to truly believe it will hook and, of course, we know it will. You and your body have to allow it to hook. Confidence in many levels or factors of your game is an essential. If you don't have faith in you, no one else can or will.

Devices:
- Lead with your ring finger. Keep it facing your target all the way through the arm swing.
- Lead with the open part of your elbow, the inside crook of it. Keep it facing your target all the way through the arm swing.
- Keep the palm of your hand facing your target ... same as above.

Keep your hand movements to the barest minimum. The more you do, the more there is to go wrong, and the more intense and continuous practice is required to keep everything in synch. KISS is part of the "bible" of bowling.

You can't tell yourself "NOT" to do something, because your brain never hears the "not" or the "don't". You have to use positives.

Since you know you're turning the ball early, one thing you could do in practice is to, once you've delivered a good ball, one that you know you didn't turn early, think back during the arm swing of how you felt and what you were thinking at the time. Learn to teach yourself the memory of the good release, the good delivery. Think of how it feels. During practice you don't have to worry about scores; worry, practice feeling (with touch, not emotion)  the good release.

I have little doubt that when you do turn the ball early, you're not focused on the bare necessities. Some other thought is being added or subtracted by your brain or subconscious. You're not allowing yourself to just "do it". You may be thinking of too many things. I'm not sure what it is, but you should know or learn what is distracting you.

 Lead with the ring finger and try to keep the ball on the inside of your hand, not your hand on the side of the ball.
 

 Wrist devices can be a good teaching aid, or help with an injury. That being said what will happen is we start rolling our forearm around the ball, the entire time we believe we are staying behind the ball.

Working hard on this also with some of the tips given above by a friend. I find that when I practice my one step drill I really stay behind the ball even more while doing this drill so the drill has many things that help my game. I was able to raise my track to within 1 inch of my thumb hole at times. Friend watched me in league the other night after a practice session and said I was at 60% good on my release...more practice as he wants to see me at 80% very quickly and I think that can be achieved.

Take a softball.  Rest it in the V between index and middle finger.  Keep that V in the same position (under the ball) through out your swing.  Start with little swings, then increase gradually to full swings.  Will teach you to open your shoulder.

I've pitched slo-pitch for a number of years now and that never helped me. Maybe doing the drills as you suggest would. Lots of people make comments about my pitching style saying it looks like I'm bowling. Oddly enough, I probably have better bowling form pitching.

Another drill that hasn't helped me is the underhand football toss. I have no problem throwing a football with a ton of revs underhand. But translate that to a 15lbs bowling ball? No.

For me, switching to a two handed release has actually helped my one handed release. I have no trouble going back to a one handed release when I'm too sore to bowl two handed (which has been happening more often recently). I'm actually throwing the ball better now. Funny that 5+ years of seeking out advice from others resulted in little progress, but bowling two handed off and on for 2 years has - and hardly any coaching.

Beyond that, I also find the suggestions listed earlier in the thread to help. When I notice I'm not releasing as I would like, I focus on those things - primarily the elbow technique because it is easy to feel the difference.