A "Capture Card" for MythTV that works by calling an external program rather than interfacing with an actual hardware device. (MPEG2, only?)
The Import Recorder (aka Import Tuner) was introduced in 0.23. Originally it was designed as a developer tool for testing Myth. However, it is potentially useful in conjunction with Myth's System Events.
To add an Import Recorder, use mythtv-setup to create a new Capture Card and choose "Import Recorder" as the card type. In mythfrontend, configure RecordingStarted, RecordingFinished events to call appropriate scripts or programs to acquire the recording. Myth will treat it as any other recording with a seek table, commflagging, etc.