I keep my emergency fund in a high interest savings account. I don't know what Schwab's rates are, but if you don't care about that yield and have other accounts with Schwab, maybe the simplicity is worth it.
Why is this getting downvoted? Current return on I-bonds is 2.52%, higher than any high-yield savings that I know of. It compounds semi-annually, tracks inflation, and there are no penalties for withdrawal. Seems perfect for an emergency fund and less hassle than a CD ladder. I'm not shilling an investment product, it's available direct from the US treasury:
It's not a bad idea. I've thought about migrating to I-Bonds. I've kept it in a savings account for the liquidity, but if you are okay with having a less liquid emergency fund, go for it.