It might simply mean that you have misspelled the command name, or are trying to use a command that is not installed on you device. I use 'developer' edition Android phones that don't need to be rooted, and I don't have any interest in hacking phones. How to Change MAC Address in Android Devices I've written a brief, incomplete, guide to using the built-in Android shell: Android Shell Command Reference. If you don't know what all that means, and why it's cool, then this probably isn't the program for you. This lets you run various Linux command line utilities. It is useful for accessing the Linux command line shell that is built into every Android phone. A terminal emulator is a program that makes your Android phone act like an old fashioned computer terminal.

Unfortunately Google Play does not allow applications that start with the word 'Android'. The name was changed due to Google Play branding guidelines.