Social Security and Medicare Lock-Box Act This bill establishes (1) in the Federal Old-Age and Survivors Insurance Trust Fund, a Social Security Surplus Protection Account; and (2) in the Federal Hospital Insurance Trust Fund, a Medicare Surplus Protection Account. The Managing Trustee of each trust fund (in both cases, the Secretary of the Treasury) (1) must transfer the annual surplus of the trust fund to its respective account; and (2) may not invest the balance in the account until a law takes effect that authorizes, for amounts in the trust fund, an investment vehicle other than U.S. obligations. The bill establishes in the executive branch a commission to study the most effective vehicles for investment of the trust funds, other than investments in the form of U.S. obligations.