Control Spotify or iTunes on your Mac from your iPhone, even when connected to a public network.

Install the application to your Mac and start it. It will appear to close, but will still run in the background. On your iPhone's Safari, head to tiny.cc/remotectl and add it to your home screen. Type your Mac's name into the text box (find it under "Sharing" in System preferences). Whenever the application on your Mac is running, the app on your iPhone can control your music player. You may want to add the application to your login items, found under "Users & Groups" in System Preferences.