You can do it anywhere, anytime, at any intensity. It's as easy as taking a walk around the block, or as challenging as 50 pull-ups. You control the difficulty, handicaps, and every aspect of the activity. Bonus attributes are it's addictive. Once you do it long enough, your brain will begin to encourage and reward this healthy behavior. Sometimes, it will even punish you for trying to skip exercise with negative emotions and nature's great motivator: shame.
The best TV infomercial for mental well-being would be a 72 point font that reads: "turn me off and get off your butt!".
EDIT: If you want some help or initial instruction, there is an app for most smartphones that can help you get started at any level. There are many variations of this type of app, but I like the "Johnson & Johnson 7-minute workout" one. You can customize it way beyond 7 minutes, and it has helpful video instruction and voice prompting. Link to homepage: https://www.7minuteworkout.jnj.com/