See their announcement here.
Sprint is investing heavily in WiMAX, which will offer a high-speed wireless network for mobile devices comparable to the broadband speed you’re used to with cable or DSL, and will reach a planned 100 million people next year. The move is significant because mobile browsing has been hampered to date by the slow wireless networks existing today. It’s a big move for Google, which has been investing in communications. The deal may let it become a default starting place for users of the nation’s third-largest mobile carrier.
It’s also significant because Sprint has pushed forward with location-detection technologies, which provides Google with more powerful ways to interact with its users. Sprint, for example, recently signed an agreement with another company, Loopt, which will let friends track the whereabouts of other friends. Google’s mapping and other technologies could find further enhance these sort of interactions.
Under the accord, Google will provide the search services for the portal, and Sprint will integrate Google’s GTalk chat service.
It’s worth noting that Sprint’s WiMax network faces rivals. The other carriers are also building out their own high-speed networks.