I own a tomtom go and I was able to customize to load my own voices which is super easy, sorta just drag and drop the files onto the device and so I wanted to share how this can be done for the iphone also.

I have swapped out dozens on voices on the iphone tomtom app, they are 100% compatible as I've installed, used them with no problems.

Assumptions - you already must know how to jailbreak and ssh into the iphone and have access to tomtom voices. Also requires the tomtom app.

steps ( note this works on any version of tomtom for the iphone)
1: connect to iphone via iphonebrowser or WinSCP
2. navigate to the private/var/mobile/applications folder and find the tomtom app folder
3. go into /us-canada.app/voices folder
4. drag and drop your custom voices you want into the voices folder
5. rename a voice you dont want to use, and rename the new voice to match the name that was there, below is an example

Here is where some minimal work is required, simply rename data00.chk to data00.chk.org and do same for data00.vif to data00.vif.org, you are simply backing up the original file in case you change your mind, simply delete your custom file and rename the original file so all is back to normal. if the custom voice filename is data80.chk and data00.vif then rename them to data00.chk and dataoo.vif

data##.chk is the voice data
data##.vif is the descriptor for the voice file

the tomtom app comes with alot of voices mainly foreign languages.

The one thing I've not figured out and maybe someone can help me is how to change the names of the voices that appear on the list? that I dont know how to do. so when you rename the file, simply select Dansk - Brigitte

my advice is go by the first ones on top
Afrikaans - doreen - data164
afrikaans - nelson
Bulgarian - marius data43
Cantonese- leiping
Cestina - miloslav data41
Dansk - Brigitte - File data00.chk

just keep in mind, when you pick dansk brigitte your are picking file data00.chk which is the file you just modified and is your new voice.

when i figure out how to make the voice list display the real modified name i'll post it back here.