There's a similar method to get into an Eight Sleep Pod 3 [0]. This requires less extra hardware though since some models come with a MicroSD card that you can modify. The method used in TFA might be a good way to get root on Pods without the card. That being said, I just learned that while Eight Sleep does sign their firmware updates, they also send you the private key used to sign the update in the same package. [0…
Don't get me wrong $2-4k is steep, but if it's a one-time for a decade or so, that's reasonable. But $4k plus you want $25/mo? Just fluff right off.