A limited version of the excellent i41CX calculator was posted last night to the Apple App Store for the iPhone (and iPod Touch). This version is FREE and might only be available for a limited time. This limited version is not programmable, has a limited function set and does not remember any data (volatile memory) when the app is exited. Even with these limitations, it is a great RPN calculator and allows you to evaluate the application to see if the full version will meet your needs. Did I mention it is FREE!
More info here:
http://appshopper.com/productivity/i41-rpn-calculator
Thanks Antonio!