I know. Why would you want to carry around your 3G iPad 1 like a giant iPhone? Not only would you look like a dork holding the thing up to your face, but it doesn't fit in any but the largest anorak pocket, no vibrate mode, and, well, why?
I did it more out of curiosity and boredom than anything else but since then, I've come up with a few scenarios that provide weak justification.
1) You use bluetooth headphones for calls and your phone is is your bag most of the time
2) You mostly text anyway.
3) You've only got NZ$749 saved and that's how much refurbs are at the NZ Apple Store (http://store.apple.com/nz/product/FC349X/A?mco=MTkwMzg4NzM)
OK, forget the justifications, here's what you do.
1) Jailbreak iPad with 4.3.3 firmware(Not condoning, just stating)
2) Add http://apps.iphoneislam.com/ to Cydia Repo
3) Install PhoneIt-iPad-4.3.3
4) Run it and follow link to iphoneislam website. I know it sounds religious, but it isn't. These are the guys who made FaceTime work on 3GS iPhones (provided you have a mirror handy)
5) Pay the US$19.95 (NZ$24ish) to activate it. I've lost some of you now. See you later.
6) The app is linked to your iPad serial number so you should have that handy. Run the app again and follow directions to activate and ultimately reboot the iPad
7) When it reboots, you'll have Phone and Message apps and all the options in Settings
Well, everything worked pretty much as it should. but some niggling problems did surface.
1) You need to use a sim (or cut one down) that can make phone calls. I had an official iPad vodafone microsim that didn't work. I swapped it for a cut down 2degrees sim which was fine.
2) I had my iPad side switch in rotation lock mode (in Settings:General) and I couldn't figure out why my iPad wasn't ringing when someone phoned. It was coming up on the screen as a call and I could answer it, but no ring. I fixed it by setting the side switch to mute mode and it was all OK.
Whatever you set the ring in Mute mode will stay, even if you switch back to rotation lock mode, but now that it was a phone, mute seemed like a better option. You can always rotation lock using the double tapping the home key and going all the way to the left and tapping the rotation lock icon.
3) Not surprisingly, the phone app goes directly to speaker phone mode unless you have something hands free setup or plugged in. Because it doesn't have a proximity sensor you have to adjust the volume down quite low to comfortably hold up to your ear and you wouldn't want to have long conversations like that anyway.
Some unintended benefits did arise:
1) Now that it has a proper number, you can use Viber or perhaps other "iPhone only" apps
2) Txting with a larger keyboard is handy.
3) I had to send a number of texts after the earthquake and plugging in a USB keyboard via the iPad Camera Connector meant I could type a lot faster.
I haven't really researched what they intend to do in the future but I do wonder if a version will be out for iOS 5? I also wonder if I can transfer it to another iPad?
If you've got a jailbroken 3G iPad 1 already, It's definitely worth $24 just for the shock and party trick value. Operationally, it does everything it promises to do and once installed, it looks like it's always been there.