How if inflation calculated for relatively new, or very improved goods?

I ask because it's a common talking point in politics nowadays that the median wage hasn't increased since the 1970's adjusting for inflation. So it made me wonder how the Consumer Price Index factors in something like a Iphone, or a flat screen tv. Phones and televisions existed 40 years ago, but were nowhere near as good. Some clarification would be appreciated

You have hit upon what is actually a valid criticism, or shortcoming of inflation measurement - that it does not account for improvements in goods.

For example, cars cost more than they used to. Inflation statistics just look at the cost of cars. The fact that cars are better than they used to be is not accounted for.

Thus some people say that inflation statistics overstate the erosion of purchasing power, because people are buying higher quality goods. To counteract this phenomenon, the BLS uses something called the "hedonic quality adjustment" in it's calculations.

The "basket" of goods that is used to calculate inflation is periodically updated to account for changes in lifestyle and typical good purchased. For example, it now included cell phone costs, whereas it did not in the past.

You can read about it in more detail here:
http://www.bls.gov/cpi/cpiqa.htm