I would stay away from the companies like "Bitcoin IRA" that are offering this. I've been told that the fees are exorbitant. It's definitely possible to legitimately set up a crypto-based retirement account yourself. You just need to find a CPA that knows what he's doing.

Personally, I'm just focusing on investing in coins at spot right now. Institutions are largely waiting for liquid, regulated markets, so we still have time to accumulate from the spot markets. In time, there will be ETFs for Bitcoin, Ether and other major coins. We should be able to roll those into our existing 401ks pretty easily.