Really the only way I'll beleive this is even remotly possible is if you post a video. Besides -
Post scale - $15.00
iPhone - $299.00 plus associated cost
If you're that hard up, get a postal scale and don't use your phone for deals.
Get off the high horse buddy. The screen not being pressure sensitive was duly noted (and your post with big text was obnoxious), and your third point doesn't even make sense, as he didn't object to the thread continuing.
Likely the same way as mentioned before. Vibrating and using statistical test to measure the difference in phone acceleration with different weights present.