As some of you may know, and all of you ought to know, exercise is good for you.
Language learning is also good for you, as apparently it staves off dimentia. So, walking and learning, exercises both body and mind. What's not to like?
Granted if you hate both exercise and languages then this won't appeal.
I walk my dog every day, and use the time to exercise my mind, or less pompously to listen to podcasts. My Spanish comprehension is good so I listen to podcasts designed for native speakers - one I particularly enjoy is 'De Pelicula'.
There are podcasts for beginnners and intermediates, for example, News in Slow Spanish which does as described, and delivers the news ... slowly. There are also grammatical explanations. You can listen to the first five to ten minutes of each podcast for free. Another possibility is SpanishPod101 which although a subscription based resource has a certain number of free podcasts available.
Looking for suitable podcasts at a beginner level can be unrewarding and time-consuming. I have an iPhone and use the podcast app to search for podcasts, but normally when I have time to waste. This is an area where paid services such as News in Slow Spanish or SpanishPod101 are worthwhile - at least until you can listen to native content.
I'm a big fan of learning complete sentences and there are thousands of Sentences in various languages on surface languages - including Spanish.
But at the moment, you can't take listen to these as you walk around. A product I would recommend for any serious language learner (who likes learning complete sentences) is Glossika. Glossika consists of a series of several thousand sentences in mp3 format, which together cover a very wide range of grammar and vocabulary. These come as mp3's and are a very useful addition to language learning.
It would be easier for you to read about the system and try it from their website rather than me try and explain it her, but the useful part here is that the mp3s repeat the sentences that you are trying to learn. This is ideal when dog walking (for instance).