The perfect in-law apartment. Or spare room. Or home for your millennial who flunked out of college or can't find a job "in his field."

My wife and I dream of the day when we can purchase a slightly larger house. We're missing two or three rooms in our current home, including a spare bedroom for when the in-laws or anyone else wants to stay over for the night.

"Granny pods" already exist, but that moniker is misleading. They are essentially small, permanent structures in your backyard.

Little houses. Fancy sheds. 

This is fine if a parent is actually moving in with you permanently, but if you're looking for something slightly less permanent and more versatile that will still do the job, I may have found an answer.  

The Ecocapsule is an egg-shaped, wind- and solar-powered microdwelling from Bratislava, Slovakia–based Nice Architects that is billed as a portable tiny home, cottage, pop-up hotel, or emergency shelter that doubles as a charging station for electric vehicles.

This is a granny pod in every sense of the word. 

First, it looks like a pod, which is amazing, but also, it's a temporary, mobile, multi-use structure that will keep your guests warm and cozy and out of your hair. 

From the reading that I have done, this pod seems to be designed for more extreme weather than is perhaps necessary, which makes me wonder if there is a business opportunity here:  

A self-sustaining pod, similar to the Ecocapsule, but not necessarily equipped to keep inhabitants alive on a mountain peak or in the Russian tundra. Something less robust that would be perfect for overnight guests, an in-law apartment, or a place to send your 19 year-old son when he flunks out of college and returns home, hat in hand. 

I think I'm onto something.