From the FAQ:
What does 2 - 4% APY mean?
APY, or Annual Percentage Yield, is the annual growth rate for your money. Every approved Beam customer will receive a 2% APY guaranteed "base rate", which is already hundred-times-better than rates offered at Top 4 US banks. You can earn 4% APY if you use other (free) features offered by the Beam mobile app
So it looks like they want to be a standard high interest account (2%), with an additional up to 2% interest for using additional features that are supposedly free (likely some kind of coercive advertising that gets you higher tiered interest by buying from their sponsors).
I doubt it's worth the trouble, but I'll be interested in hearing what your opinion of it is if/when they start taking customers.
