Here's the thing, if you are merely interested in losing weight then a scale is fine, if you are interested in recompositioning your body then a myotape and mirror are better.
Mirror explained
Affix the full length mirror to the wall.
Put a mark on the floor where you will stand each and every time.
WIth someone to your side have them mark with the grease pen on the mirror where your outine is for the shoulders, waist, abs, thighs.
This gives you a visusal cue to your progress and also represent what others will see and notice.
Actually your waist is under your last rib(the narrowest portion of your torso), your abs are at your beltline, inline with your navel, or just above or below depending on where you wear your pants. If you wear them under your armpits then.........Get a Life.
Anyway wherever the greastest compositional change needs to happen (waist vs abs vs hips) this is what you should mark.