It you have already blocked someone on your GTalk account and want to check the blocked list and see blocked friends on GTalk for Android phone and devices, do as follows:
1. Open "GTalk" (If you haven't updated to Google Hangout yet!)
2. Hit "Menu Button" and go to "Settings"
3. Select the Google Account you want to see it blocked list
4. Scroll Down, and under "Account" tap "Blocked Friends"
5. There you can see the friends who are already in your Black List!
Note that, we couldn't find a way to block friends on Android devices. For now you need to block them from your PC or Laptop.