Most banks support this I thought - just mail a deposit slip and a check (signed, with a "FOR DEPOSIT ONLY" endorsement) to the right address. I've done it before with ETrade Bank and ING Direct at least, and I imagine brick-and-mortar banks would do this processing if you mailed the check to a nearby branch.
I get quite a few checks, but not enough that I'd want to get a check scanning machine for.
I'm on the beta list, and hope for an invite.