Thanks for the replies everyone. I didn't dare to check for a while because I thought it didn't have any replies.
Hi there! A good idea, a very good one actually but maybe because people need to see it work across several sites. I'll give you a few to start off with, based on where I've played dice or know dice is popular:
1. Crypto.games
2. Bitsler
3. Bitvest
4. 999dice
5. Fairlay
6. Yolodice
7. Freebitco.in
It could be tricky but if you could really interface with regular casino software:
1. Sportsbet
2. FortuneJack
3. Bitcasino
4. Bitcoinrush
5. Betcoin
Get your code open source too. And have as much detail as possible for a newbie to understand how your extension verifies provably fair (maybe even a tutorial inside to teach them) and you might have something on your hands. Don't worry, new extensions will be difficult to break through as people rightly won't trust it. Maybe work with a couple of owners to suggest your extension.
Thanks for all the suggestions! I was planning to integrate more sites but got a bit discouraged to be honest. I will follow on with some of your suggestions. The library code is already open source but I will open source the UI code as well after some cleaning up.
I think the open source aspect is enough to discourage people and you. Betting sites owners/admins need to be very sure what they are allowing on their sites.
I really like the post on your provable fair extension. Just hope the code transparency issue is addressed before I could encourage people to try it out.