If you've ever needed to send a file to somebody, but it was too big for e-mail or DropBox, you may have looked at services like YouSendIt. However, if you're concerned about the file being stored on a third-party server and somebody other than the intended recipient getting it, then perhaps you've been wary of services like that.
If so, then justbeamit is for you. It initiates a peer-to-peer connection between you and the recipient, allowing you to monitor the transfer in real time and avoiding the need to store it on a server somewhere. Once you close your browser window or navigate away from the page, the link to the file is invalidated.