T-Mobile International, which is currently using Wi-Fi for its convergence offering in the U.S., has disclosed an investment in Ubiquisys, a maker of femtocells. T-Mobile also said it was trialling the startup’s femtocells in Europe. Femtocells, which plug into an existing broadband connection to provide a signal in places where mobile network coverage is poor, are getting their day in the sun. Google, Accel Partners and Advent Ventures are also investors in Ubiquisys, which has raised $37 million.