On the iPhone you can start the diary mode in myTracks. This always records a new track point when the iPhone moves significantly. For diary mode, myTracks uses a special iOS feature that detects these significant location changes and then informs myTracks of the new position. An advantage of the mode is that myTracks is informed by iOS even when myTracks has been stopped or when the iPhone has been restarted. Whenever myTracks has been informed, myTracks activates the GPS for a short time in order to determine the most accurate position possible. This means that every point recorded in diary mode should be as accurate as possible because it was determined using GPS. iOS detects the significant location changes based on the existing cell phone towers and wireless networks. Unfortunately, the consequence is that significant changes in location only occur sporadically, depending on the environment. The advantage is that there is hardly any strain on the battery. This means you can activate diary mode once and always leave it activated.
myTracks users would like to record points more frequently in diary mode. Unfortunately, due to the way this mode works, as a developer I currently have no option to have more points recorded. Maybe there will be more options in future iOS versions.