For a long time, I kept my active Next Actions in Omnifocus and my potential (someday/maybe) actions in Evernote. It worked, but it felt a bit cluttered so I moved it all into Omnifocus.
I don’t have a daily commute but I still find myself in the car having ideas from time to time. I don’t want to lose those ideas, but I shouldn’t be typing into my phone or writing things while I’m driving.
OmniFocus is a powerful tool designed to follow David Allen’s Getting Things Done. I go into the details of GTD here but the simple version is that it’s a method of getting things out of your mind and into a trusted organizational system. The main purpose is to free up your mind to have ideas, not hold them.