I've developed an iOS app the last two weeks to fix the problem for organizing meetups to fight in raids together for Pokémon GO players. It was released today to the App Store, it's completely free (and even open source) so you're welcome to check it out:
My goal was to provide a way to meet up for raids in a way that is safe and transparent. You can provide gyms & raids right within the app and organize meetups. Also, you can find and attend meetups organized by others. There's even an option to set push notifications on specific gyms so you don't miss any meetup.
The project is open source (both the app and server) and currently is and always will stay ad-free. See the official project page for more information:
Of course the app will only be useful if many players use it, so spread the word!
Any feedback or ideas can be provided via our official forums: