Amazon.com chief Jeff Bezos' personal investment firm has bought out Expensewatch.com. The company, based in Conshohocken, Pa., sells software aimed at helping small businesses control and reduce their operating costs. Its signature product is a Web-based subscription service that tracks travel and entertainment, purchasing and other expenses.

Bezos' investment company, Bezos Expeditions, was already an investor in Expensewatch.com and has two board seats there.