Google Wallet is an app that lets you pay for purchases using the NFC chip in your Android-powered smartphone on special “PayPass” credit card terminals — but it is only “officially” available on the Sprint Nexus S 4G.

Nexus S 4G

If you want to run Google Wallet on your Sprint Nexus S 4G, simply download the Google Wallet app from the Android Market and you’re all set!

If you want to run Google Wallet on another device you’ve got some work ahead of you.

In this video we’ll show you the app working on a GSM Nexus S and GSM Galaxy Nexus. If you’d like to get Google Wallet on your “unsupported” Nexus S or Galaxy Nexus, we’ll tell you how to do that after the break.

Nexus S (GSM)

If you want to run Google Wallet on your GSM Nexus S you’ll need to unlock it, root it, flash a custom recovery ROM, and load up supported custom ROM. Currently CyanogenMod nightly 212 and above should work.

That’s where things get sticky.

Boot into recovery mode (by pressing the volume-up key and the power button) then select RECOVERY, then wipe everything (data/factory reset, and cache). Yes, this will erase everything on your device. Next, flash Cyanogenmod nightly 212 (or higher), which you can get here: download.cyanogenmod.com/?type=nightly&device=crespo.

After you’ve flashed the ROM you have to flash the Google Wallet package (before you flash GAPPS). Next, flash GAPPS, then reboot.

After you’ve booted, run through the initial setup, making sure you setup your Google Account, then launch Google Wallet. It will probably force-close — don’t panic! Open Google Wallet again, and start the setup. Once that’s done you should be able to use Google Wallet on your Nexus S.

Galaxy Nexus (GSM)

If you want to run Google Wallet on your Galaxy Nexus you’ll need to unlock, root, and install ClockworkMod Recovery. Luckily, we’ve got a tutorial that tells you just how to do all that: How to Unlock and Root Your Galaxy Nexus. (Remember, OEM unlocking will wipe your entire phone, data and system.)

Luckily, this version doesn’t require a special,multi-package flashing process, but you will need to fix permissions if apps start misbehaving (which they probably will).

After you’ve unlocked and rooted your phone, set it up (including your Google Account) then reboot into recovery mode. Flash the Google Wallet package, reboot into Android (this will be slow), reboot into recovery mode, run Fix Permissions, then reboot into Android again.

Lastly, launch and setup Google Wallet.

If you want to try either of these, we’d love to hear your success stories, and reactions of people who see you paying for stuff with your phone!

Enjoy Google Wallet!