According to Register Hardware, "OLO promises Foleo-style iPhone-Air laptop combo" (Tony Smith, 13th October 2008 10:50 GMT), company OLO is promising a netbook small notebook computer into which an iPhone fits. They are skeptical as to if this is a real product. It has some appeal. What might make more sense is a desktop iPhone PC.
Some months ago I went into the new Apple Store in Sydney and asked if I could plug a keyboard and screen into an iPhone, to make it a desktop computer. The staff looked at me sceptically and said they thought not. After some hunting around they found there was an adaptor for plugging an iPhone into a large screen. The iPhone also has a USB port and this should just need extra software to support a keyboard and mouse. What this would make possible is for that you could plug your iPhone into a charging cradle and then use it as a desktop computer with a large screen and keyboard. However, this would be hampered by the iPhone's limited memory and processing capacity. What might make more sense would be a low power low cost nettop computer which the iPhone would be plugged into.
A netbook could be similarly designed to slot in an iPhone, but it is not clear what advantage this would have. The netbook will have little extra battery power to recharge the iPhone and the iPhone touch screen will be little better than a netbook's pad. You might as well save all the trouble of a new mechanical design and link them with wireless.