OK, so I have been trying to get google voice setup in a nice way to work on my Tattoo and once I completely figure out what the hell I did I'll be sure to post a full walkthrough.
I tried like hell to get the apk file from anywhere online. Google would not provide the file so I decided to turn to the only other android device I had: the SDK emulator on my Mac.
The avd I was using was modified to be able to download content from the "normal" marketplace. I downloaded and installed the Google Voice app and started to wonder if I could open the userdata.img file. luckily, I didn't have to.
With the emulator running:
$ ./adb devices (to get the emulator ID)
$ ./adb -s emulator-XXXX pull /data ./ (dump the data folder to the previous directory on my computer)
I then quit the emulator and connected my Tattoo:
$ ./adb install com.google.android.apps.googlevoice.apk
So let me save you all the headache and simply say...
this is where you can find the Google Voice APK file
But I think I might be onto something that will give easier access to non-tattoo approved apps in the Market place.