My kids have threatened to do this, but have never actually swiped my iPhone so they could use my Starbucks app to buy things for themselves. I trust you made your son pay you back for the cost of the thermos and VIA packets? I'd have charged an additional 50% stress and rudeness tax on top of the base cost, personally. :-)

The Starbucks app is definitely a winner if you even go to Starbucks once in a while. If you're a regular, like I am, then it's great, helping you earn and keep a gold card which gives you free special milks, flavors and other upgrades and, as you note, tracks the buy-15-get-one-free promo they're always running. I get a free beverage card about every 3-4 weeks now...

Apparently you're not the only person who has had an issue with your Starbucks app, and the software does include the ability to set an access password, though at four digits, it's not the most secure code in the world. I use it in case I lose my phone (I don't need some stranger tapping "add $100" and buying a few coffee makers to later sell on Craigslist!!) but my kids know the code. For now. We'll see what happens down the road!

To set up your access code, launch the app, then tap on the "Home" button on the lower left edge. You'll see a bunch of options:

Tap on "Settings", as conveniently highlighted in the above image.

Now you'll see the surprising number of options you can set and modify:

If you guessed that you should tap on "Passcode", then I can only conclude you've had your morning caffeine. Well done!

Tapping on it brings up a numeric lockpad, similar to what you see if you've set a time lock on the phone itself (and you should set that up!):

Note the warning: "If you set a passcode, you'll need it to use this Application." Don't forget what you choose. Enter all four digits and it'll ask you to enter it a second time to confirm:

Got them both right? Then you're done. Go to a different app, then tap on the Starbucks app icon again and instead of going directly into the program, you'll see this:

I find this very useful and remarkably little hassle. I hope you do too. Oh, and don't let your son touch your phone again! :-)