Whatever Apple will allow. At the time of this writing, if you download Call Now using your iTunes account, and if there are several iPhones sync'ed with that account, they will all have Call Now, although you may have some issues with the phone number that Call Now calls, if the installation of Call Now on each iPhone is set to call a different phone number. Adjust after sync, as necessary.

We suggest that you place the Call Now icon where it is most directly accessible without you having to think about it. To move the Call Now icon, hold your fingertip on it until it starts to writhe with demented pleasure, then drag it with your fingertip to where you want it on the screen.

While the icon is happily writhing, if you touch the circled X at the top left of the icon, your iPhone will ask if you want to delete Call Now. We'd rather you say no. Some people get into this situation accidentally, and wonder what's going on. Press the home button below the screen to escape the deletion.

No, those devices don't have a Phone application built in. We tested Call Now on an iPod touch, one night when we were very tired, and proved this. If you bought Call Now, it would only be useful after you bought an iPhone as well.

We addressed this in the iTunes App Store description for Call Now, in several places. We tried to make it prominent. Not everybody reads the description. What can you do.

Current issue, to [censored] who trashed every app in this category but one, in the U.S. App Store reviews: which end of your iPod Touch or iPad were you planning to speak into? We will deal with this later.

For the record, the "compatible with iPhone, iPod Touch and iPad" accompanying the App Store description of Call Now, is an artifact of technical issues that were present at the time of release of the app, that are not public and are beyond our control. Your iPad and Touch are not cell phones.

Our backgrounds are in mathematical modeling, physics simulations, database development, AI game engine design, gaming systems, and productivity applications, on various operating systems.