An Iphone 4, pretty much using Li-Po 1420mAh, 137 g in total weight (Stainless steel + glass), 115.2 x 58.6 x 9.3 mm dimension.

If Apple can do it then why can't Nokia try to do the same? Shrink everything and start using MicroSim, slim down the battery but make it wider flatter, slimming down the keyboard hardware to use thinner matterial.

I am sure that it will be at least 30% slimmer than N900.