Before You Get Started...

A few caveats:

• Jailbreaking, the process of opening up your phone to allow for the installation of unapproved 3rd-party applications, voids the warranty on your phone. If you're a stickler for these types of things, this may not be the hack for you. (If you really want a phone that functions as a Wi-Fi hotspot, maybe you should wait for the Evo instead.)
• That said, jailbreaking is reversible in the sense that you can always return your phone to factory settings then reapply your backup and no one will be the wiser. Your iPhone is automatically backed up every time you sync with iTunes, but you may want to double-check that your contacts, photos, calendar items and any other critical information is safely stored somewhere else...just in case.
• The MyWi app is buggy. Really, really buggy. Upon first launch, it crashed repeatedly in our tests. The issue seems to be with the "Rock You" sign-in/registration process. But I got it working and you may be able to as well. In fact, it's the crashing problem that makes the entire setup process take so long - not the jailbreak itself. That's downright speedy.
• MyWi isn't free, but comes with a trial period (thank goodness!). The app costs $9.99 when you're ready to purchase.

How to Turn your iPhone into a Wi-Fi Hotspot

1. The first step is to jailbreak your phone. If you've never done this before, you can follow our guide here for the iPad - it's the exact same procedure, from start to finish. For those who are familiar with jailbreaking and just need the software, go here: spiritjb.com.
2. Once your jailbroken phone is up-and-running, launch the Cydia application store.
3. In Cydia, search for "MyWi." There are two apps listed, but the one that says "No Rock" next to it never installed for us. Grab the other one instead.
4. Tap on the search result for the app, tap the "install" button in the upper-right corner, then tap "confirm."
5. When installation is complete, tap the "Reload SpringBoard" button. (If this part gets stuck, just reboot your iPhone).
6. Launch the MyWi app. Accept the agreement and tap "OK." Now comes the tricky part. In our tests, the app would barely stay open for more than a couple of seconds at this point. In fact, we were about to write it off as a total loss. But after a bit of perseverance, we got it working. It appeared as if the problem was with registering for a RockYourPhone account via the app. (RockYourPhone is a paid application store for jailbroken phones where MyWi is sold.)
7. Instead of registering for an account via the app, we went to RockYourPhone.com and signed up there instead.
8. Before returning to the app, we copied our registration email address to the clipboard so we could quickly paste it in instead of typing it in.
9. Re-launch MyWi. Tap "sign in." Paste in your email, type in your password. The app will check for your registration (and probably crash again).
10. The app will check for license updates and then allow you to use it on the "trial" license. If you can't get past this step because the app continues to crash, we're sorry. We can't help you. Like we said, the app is buggy. You may be able to get it going, but we'll make no promises. Hopefully, a future version will be more stable.
11. Assuming you do get the app to (finally!) launch, you'll see the option to turn Wi-Fi Tethering on via a toggle switch at the top. You can also turn on USB and Bluetooth tethering using the toggle towards the bottom. With tethering on, your phone's Internet connection, 3G or otherwise, is made available as a Wi-Fi hotspot to nearby computers. You can even use WEP security if you'd like.
12. When you're finished, you can switch tethering off and close the app.

Note: Problems Sharing 3G?

If you run into problems with MyWi not being able to share your 3G data connection, a simple reset of your network settings may resolve the issue. Go into the Settings app -> General -> Reset -> Reset Network Settings. Reboot the phone and try MyWi again.