6. Baby monitor.
New parents tend to splurge on pricy baby monitors. Whether it gets used is, well, not part of marketing baby products. Instead, try a $3.99 app that turns an iPhone (or iPad) into a two-way video station. Baby Monitor 3G syncs two iOS devices, turning one into the baby station, the other into the parent station. Leave one in the baby's room and it will stream live video over Wi-Fi to the parent's phone, or alert parents when the baby moves. You can also use it to speak to the baby while in another room.
Of course, an iPhone or iPad is even more expensive than a $100 baby monitor system, but if you've got an iPhone to spare, this is a good test to see whether the family would benefit from a baby monitor. Or at least you'll get a hassle-free monitor for travel.
7. GPS for the car. Smartphones with GPS systems come in especially handy when you don't have a dedicated GPS for the car. With an old iPhone, now you do. Keep its Wi-Fi on and it'll update when you pull into the garage.
This article is commentary by an independent contributor, separate from TheStreet's regular news coverage. Email Tamara Chuang at email@example.com and follow her on Twitter @gadgetress.