More than a celebrity endorsement, RZA's new partnership with Boombotix gives him a hands-on role in product development.It's 10:30 p.m. when Mustafa Shaikh's phone rings. It's RZA. It's not every night that the founding leader of the Wu Tang Clan calls his cell, so he picks up. Shaikh, the VP of marketing at portable speaker company Boombotix, is in for an earful.