I am trying to make a transportable charger for iPhones, but before I can start this I need to know how much power my iPhone uses when I make an emergency call.
If nobody knows this, I will be glad to have any information related to this.
Anandtech has some nice charts detailing the wattage of the iPhone 4S running various apps, which could be a good starting point for you.
You may also want to check out existing kits/projects, such as MintyBoost - they seem to work reasonably well with iPhones. There's a specific MintyBoost page detailing Apple device charging that may also yield some useful info.
The power use is going to vary somewhat depending on external factors on the RF side. Network mode in use (GSM/3G) and the power required to establish a stable connection to the cell site in use together with any other usage on the device (speaker/bluetooth/GPS)
Best guess is that your baseline should be the specified 1A required to charge the device and work up/down from there with a meter connected