This is how I set up my Google Voice.
I like it because it works with Universal Search and Speed Dial. I made a video of it.
Google Voice on Palm Pre
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Method 1
I send an SMS to one of my contacts, let's say 321 area code through voice.google.com. When they respond, it will show up as a 406 area code number on my Palm Pre. I save this 406 number in their contact information on the Pre as another "Mobile" number. Doing this will group the responding text message with all of the previous messages from that person, resulting in just one threaded conversation with that person.
If you text the 406 number from your Pre, it will arrive to the recipient from your Google Voice number.
If you text the 321 number from your Pre, it will arrive to the recipient from your Sprint number.
If you dial the 406 number from your Pre, your Google Voice number will show up on their caller ID. You will be charged for minutes, unless the 406 number is part of your Pick 3/5.
If you dial the 321 number from your Pre, your Sprint number will show up on their caller ID. You will be charged for minutes, unless the 321 number is on Sprint's network or it's part of your Pick 3/5.
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Method 2
If you have Pick 3/5 and you have assigned your Google Voice number to be one of them, this is how you can set things up to get free outgoing calls through your Google Voice number. It will also work if you don't have Pick 3/5; you will be charged for minutes though.
This is basically how gdial and dkGoogleVoice in the homebrew forum works.
For each contact, create another phone number like this: "(xxx)xxx-xxxx tt2t (yyy)yyy-yyyy#"
Replace (xxx)xxx-xxxx with your Google Voice number. Replace (yyy)yyy-yyyy with your contact's number.
I do this in my Google Voice Contacts page, and Synergy ports the numbers to my Palm Pre.
So when you dial this long string of numbers from the person's contact information, it will dial into your Google Voice voicemail, pause (tt), dial 2 to place a call, pause again (t), dial the number of the other person, and then press the # key to connect the call. It will appear to be coming from your Google Voice number and, if you have your Google Voice number as your Pick 3/5, you will not be charged any minutes.
It sounds like a long process, but his method will only take about 15 seconds before the other person's phone begins to ring.
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I hope this helps some of you!