We have seen the retro phone handsets that hook up to mobile phones already in 2004. Spark Fun just completed the thought and offers now a complete rotary phone with an mobile phone inside.

The Port-O-Rotary features a GM862 cellular module from Telit which works within any country that has one of the 900MHz/1800MHz/1900MHz mobile networks.
You dial numbers with the analog dial and of course the phone rings old school, when a call comes in. You will draw for sure attention when you put this phone on the table in a restaurant and a call comes in. At $499 not a bargain.
More details on Spark Fun. Via Arstechnica.