This free script allows you to easily navigate in timeline. You can change the active time segment by dragging the slider, or zooming with your mouse wheel.
Bug report: info@univerpix.hu
Version info:
1.6.1 (2013. Apr 7.) Error in new scene fixed, callback event error fixed, zoom to selected keyframes works with biped objects.
1.6 (2013. Mar 19.) Available to Zoom to selected keyframes.