I use bike rides for your walks approach, though sometimes (say commuting) I get to my destination without remembering how I actually got there; the day dreaming is perhaps a little too immersive (some of this might be pretty busy city riding!) but in less attention-critical scenarios (like a ride outside the city, on the pathway or the grind up to a DH track) I have my absolute BEST periods of thought. Doing something you like (or in my case love), not using your phone, and getting exercise - especially in nice weather! - is a super-power. I know that if I get to a conclusion in this setting it is likely one of my better ones.