If you love something, let it go. Then track it on your iPhone.

Sometimes it’s hard to tell when someone is pulling our leg. This promotional e-mail struck me as a joke, but on subsequent readings I’m not so sure. The ad is selling an iPhone 4 app that lets you … um … confirm your family’s whereabouts. You know, to be sure they’re safe:

“Family Tracker allows you to track your wife, husband, children and fiancée 24/7 using the new multitasking feature in the Apple iOS4.

“The new Family Tracker runs in the background on the iPhone, constantly updating its GPS location. Spouses can thus instantly know their partner has safely reached their destination at home, work or during long trips. Parents can know if their children are exactly where they should be, and didn’t sneak out without permission. … Privacy concerns are nonexistent, as the owner of the iPhone has to give prior consent in order to be tracked. Family Tracker allows peace of mind [by] letting you know where all your family members are at all times.”

That’s a nice touch, including the “fiancée” among the people you might want to track. Another nice touch is dismissing the obvious privacy problems with a breezy assertion that the target – excuse me, the fiancée – has at some point agreed to the deal. The agreement, we can assume, was the price of getting the Coolest. Phone. Ever. Made.

Dad: Honey … kids. As you were. I have the phones you requisitioned. Before I issue them to you, I’ll need you to click “I agree” on the “Family Tracker Target Consent Form.” Then I’ll be able to pinpoint your location anytime I don’t have a visual on you. This is for my peace of mind.

Great idea! Let’s use technology to take the guesswork out of relationships. Who needs trust and accountability, when you have an iPhone 4 with a killer app?