I was wondering if anyone thinks it would be possible to write an app for the iphone that would log your outgoing calls & SMS usage?

I am thinking seeing as the phone already logs mobile data usage and total call usage those features wouldn't be required.

It would be nice to be able to monitor how one is going within one's Cap plan seeing as Optus doesn't allow live tracking of your usage.

Would it be possible to write that info into an app? Or is it impossible because the iphone doesn't allow background processes, which would be required for a log file?

I don't think this is possible. Someone else asked in a previous thread. There's just some functions on the iPhone that the SDK doesn't have access to, plus it can't run in the background as you said.

Thats all I want, an SMS count.

i want a simple mms app so my phone is as useful as a 10yo nokia....

App that vibrates when you go faster than a certain speed. (for riding on motorbike)
App that makes sound when you go faster than a certain speed only if there is a speed camera located within 100 meters. (for cars)
App that alerts you when 5 minutes before it is about to rain. (using weather radar and current location)

App where you take a photo of anything, all the text inside the photo is automatically translated to your preferred language.
(Not original, Nokia has demonstrated this on the N95)

App that reads out text you move the camera over.

App that reads out text you move the camera over automatically in another language.