MindMeister offers an app for the Apple Watch, called Geistesblitz, which lets you capture ideas and thoughts with your watch, and send them to your MindMeister account, where they are inserted in a mind map of your choosing.
Note: Aside from the Apple Watch, all other Geistesblitz features have been discontinued.
Once you've added Geistesblitz to your Apple Watch, you can start recording ideas:
1) Tap "Add Geistesblitz to" to select the mind map in which your idea is to be inserted.
2) Browse your folders and maps and until you've found the map you're looking for, then tap on it.
3) Tap the white Geistesblitz button (with the lightning symbol) to start the recording, and speak your idea into your watch.
4) Tap "Done" once you're finished. The idea will be inserted in the mind map of your choice immediately. You will be able to view it on your connected smartphone or iPad as well as MindMeister's web app.