SeeYou Navigator will help you stay centered in the core of the thermal. When it detects that you are thermalling, it will automatically zoom in to the map. The track will be displayed and colored so that you can easily see how the thermal is developing:
. Last few circles are colored by vario and outlined
. Last few minutes of the track is colored but not outlined
. The rest of the track is a thin gray line

Map will automatically return to the previous zoom level once you stop circling.