Consider the Sony Ericsson T68 released in 2002, probably one of the smallest phones to hit the mainstream. It weighed only 84 grams (about 3 ounces) and was easily shorter and narrower than any smartphone today. Phones today are big flat slabs of glass and they are getting bigger.
FierceWireless has put together a report of various phone statistics over the last year and there is a clear trend. If you go all the way back to September 2009 and look at the phones released that month, the average thickness was 15.16 mm, or 0.6 inches. As you look at the last 12 months, you'll see the average thickness decline to just under 14 mm. The iPhone 4 is helping to bring that average down with its svelte 9.3 mm depth.
Screen sizes are on the increase, which should come as no surprise. In September 2009, the average size was just 2.85 in. It has grown to an average of 2.97 in. The iPhone 4 has a 3.5 in. screen. That is nothing though compared to the HTC EVO 4G which is 4.3 in. across.
With larger screens comes heavier devices. Phones are up from 103.8 g a year ago to 114.1 g now. All of that glass the iPhone 4 has brings its total to 137 g--nearly 4 oz.
What about features though? Bluetooth support hasn't really budged, holding in at around 68% for the last two years. Wi-Fi has moved from the sub-25% range in 2009 to over 50% in recent months. Part of that may be driven by carriers trying to offload some of the bandwidth to non-cellular networks when possible.
I don't see screens getting much larger. The 4.3 in. screen is about as large as you can reasonably go without wondering whether or not you have a large phone or a small tablet. Where do you think phones are headed? Will the current mini-tablet form factor continue for several more years or will user needs for things like keyboards or more compact devices drive dimensions in a different direction?