I have a new full belt that was a Christmas present and have been wearing it around the home quite a lot since New Year. With the lockdown currently in force I have not been out in it. I went out for a walk with my wife yesterday, well over an hour. It is one of the designs with a solid tube apart from the drain / vent holes at the end and is a good fit on diameter but is a bit longer than it needs to be. As I walked, I could feel the tip of my penis moving and lightly rubbing on the end of the tube with every step. It made the walk into a stretched out constant tease session as I kept getting those lovely reminders of being locked. I have never noticed this around the house where I get very little movement. It was probably because I was walking faster or it had shrunk a bit or moved into a position where the head could move.
I haven't worn a belt, but the sensation of a cage when walking outside is memorable. As you say, the constant movement makes you hyper-conscious of wearing it.
Maybe next time get plenty of (water-based) lube into the end of the tube and over the head of your penis and it'll be much much worse. Make sure your wife's aware so she can take full advantage - teasing you about your frustration or distracting you if it seems like you're going to orgasm. Actually coming in the tube in public could be interesting, as would be walking home afterwards with the tip still rubbing and now in all that cum.