Do Something With Your Hands!
We have to move more of our body more of the time in order to achieve the most robust health. So, it's beneficial to think of what other parts you can move while engaged in an activity like walking. For example, if you're not carrying anything, you can use your walking time also as an opportunity to stretch and move your arms and hands. There are numerous possibilities for arm and hand exercises.
A few possibilities are:
Interlace the fingers and turn the palms outward while reaching the arms forward and overhead
Place the back of the hands and wrists together
Stretch individual fingers
Experiment with "stacking" these exercises to get more movement of your body more of the time.