lets you tune your guitar to the tuning of your choice. Go ahead and start by selecting an input device: the best results are achieved with a dedicated sound card, but you can just as well use your microphone.
Other modes but normal are currently not yet implemented, but should soon follow.
Below you will see a field to select a tuning, and an indicator of how well a particular string is tuned next to it. For little hints, hover the question mark icons.