I don't have ANY faith in "Palm Security;" it's fine for losing your PDA at an airport and someone "friendly" finding it; however there is NO encryption. There was an optional download for the T3 available from PalmOne - and that is in fact TealLock, licensed.
I strongly recommend buying the full version of TealLock which gives you option of hide/mask, 128 bit blowfish encryption, different levels of encryption for private/public records (you could have "regular addresses" unencrypted and ONLY encrypt private records, or encrypt the whole thing) - plus encryption for any/all prc's and subsequent databases.
The program -- for example Sheet2Go -- is NOT encrypted, but all spreadsheets RELATED to it are encrypted.
Furthermore you have the option of guarding against "extraction" of information through the serial port, moving to the SD Card or whatever - by telling TealLock to LOCK OUT serial port, infrared, silkscreen buttons. You can even opt to have 2 programs RUN while locked, and have the handheld respond or not respond to graffiti on power on.
You can set it to BLOW UP ALL RECORDS after a certain number of incorrect data entries (be careful on this one) - or a "booby trap" self destruct based on an activation code for that self destruct.
The latest version of 5.47 is tremendous and TealPoint have worked out some appearance problems with the Treo and the T5. I've been using it for almost 3 years.
Backing up with a backup program such as Card Backup presents no problems either - full restore restores everything although you must reset the device (CardBackup warns you of this after restoring).
To protect only certain private information such as bank records, pin#s or other info, TealSafe is excellent - but if you don't want 2 address books (regular and TealSafe), TealLock is just great.
The only caveat I would throw in is backing up private records "protected" is IGNORED on the Palm. In other words when you backup address DB (BobContacts DB) to the card, they are UNENCRYPTED. Someone could get the backup SD Card and it wouldn't matter what you'd performed on the handheld itself. TealLock allows you to encrypt files on the SD Card as well, also at 128 bit blowfish - however you would have to use a file utility to COPY your address database to a folder on the card, encrypt it, then instruct your backup utility NOT to backup the file.
An easier solution (you can tell I'm a Teal guy) - is TealBackup. Select ONLY those sensitive files and ask TealBackup to back them up ENCRYPTED daily; strike them from the list of your "other" backup. I wouldn't bother with TealBackup doing ALL your Palm files, as it takes a little longer in 128bit and prolongs the backup process. Now you're set.
I do all of the above and it's painless and automatic; private spreadsheets and contact database are protected on the handheld and in their backed up form, too. Like you I was concerned about what "private" really was and researched around 15 different products before deciding on the above.
If you buy TealLock, TealBackup and CardBackup it'll run you around $65; if $$$ are an issue then I'd go with TealLock but hotsync often. Use a file utility like Filez or TealMover to COPY sensitive stuff to the card, and have T/L encrypt those card files (it makes it's own folder for encrypting information, so to avoid them being MOVED from your folder to the encrypted on, just put them in TealLock's own folder - not as much "data in transit" issues or chance of errors if they're not constantly being moved).
