Is there a way to do this? How safe is it?

I want to take an app's data from an older iPhone backup, slip it into a newer backup, and restore from that backup.

Reason: some important app data was deleted, and can be found in an older backup I kept, but the rest of that backup is too old and I can't restore from that. I need to restore from the new backup, with just SOME things moved from the old.

(My iPhone experience has gone from very good to very bad to impossibly worse: now every time I plug my phone in, it starts deleting apps I need... and installing ones I don't! As a result, I've lost Air Sharing--not the app download, but my data stored in it. I'm sure I'll find other apps I need to restore too--assuming I can stop iTunes 9 from going nuts like this. Maybe this latest update will help.)

Googling found this...
http://www.reincubate.com/labs/iphone-ba...be/3_wizard.png

Cool. I'm scared to try it, but I have a second plan in the works* so maybe I will (Looks to be just one piece of the process though.)

For extra fun, this is happening in the same week that my laptop died and someone just totaled my car. Which comes with a bonus: ambulance chasers calling my iPhone every 5 minutes, having harvested my number from the police report. Sa-weet!

* I'm taking screenshots of certain key info since my last (good) sync, and will email them to myself. Then I can restore from the old backup, and pick up the pieces at my leisure, if other options fail.

Well I went with plan B (operation PITA) and rolled back to the earlier backup in its entirety.

Meanwhile, though, I'm still interested in the question--it's something I was wondering about even before I needed it. If anyone has done it, I'd be curious how it went.

If the old app's data is the kind you can get off the phone in the first place (via browser/rendevous) then I suppose the laziest way is to restore the old backup, pull off the file, and then restore the newest one again.

I don't know of any apps that can hack the backup data on your mac itself.

Thanks. I went the screenshot route, and then re-entered or re-imported specific lost items from the few days since my last sync.

What's weird is every time I wipe-and-restore, something gets lost--some app is missing its passwords/login, or some little thing. But it's always different. Once my Mail apps lost their passwords. The next time no--but my WiFi logins did. Then the next time, those two were fine, but Pandora lost my password.

I keep records of all these, it's just odd. I definitely do NOT have the feeling of "trust" that you want to have in an OS. Mac OS X I "trust"--I don't have any significant fear of an unrecoverable problem. I fear my iPhone.