Using proxy servers to cache and shape network traffic can significantly improve the energy efficiency of the participating mobile clients. In this article, we analyze the implications of hosting a BitTorrent proxy on a broadband router, which pushes the content to a mobile phone over wireless radio (WLAN or 3G). The amount of memory in a router is limited; therefore, our interest is in how to efficiently use memory to download BitTorrent content as fast as possible and at the same time transfer it to the mobile phone in an energy-efficient way. We investigate these aspects via a series of measurements. The results show that the proxy-based solution outperforms the torrent client running on the phone in terms of energy and download time. We also simulate the BitTorrent operation to understand how these memory-limited devices would influence the operation of the whole community.