If someone asked you what you can do with an iPhone, you could say playing games, listening to music, watching videos and even making phone calls. One thing that you probably wouldn't mention is checking your blood oxygen saturation. But you can now add that to the list, thanks to Masimo's iSpO2 pulse oximeter.

Pulse oxi-what?

A pulse oximeter is a device that measures your blood's hemoglobin, which is the protein in red blood cells responsible for transporting oxygen from the lungs to all other tissues of the body. If you're a pilot, athlete, or if you suffer from a sleep disorder, monitoring your blood's oxygen level can be important.

Pulse oximeters provide a needle-free method of doing this. Clamp the sensor on your finger, and get an instant reading.

You can buy many (cheaper) standalone pulse oximeters, but the iSpO2 is the first that's compatible with iOS devices. Masimo's oximeters are also amongst the best-selling in the industry, largely due to a patented technology that accurately measures oxygenation while in motion.

Design and use

The Masimo iSpo2 is a simple device. The white finger-clamp sensor extends from a wire, which connects to your iPhone. It's light, portable, and comfortable on your finger.

When you connect it to your device, iOS asks if you want to allow access to the iSpo2 accessory. Grant it permission, open the free iSpo2 app, and within seconds you'll have your reading.

The app, like the device, is straight-forward and well-designed. The uppermost reading shows your oxygen saturation. Beneath that, you'll see your pulse rate (beats per minute). At the bottom, the app reveals your Perfusion Index (PI), a measurement of your pulse strength. The app also displays your pulse in a waveform graph.

The app also logs your history, and allows you to email your results as a spreadsheet document.

Compatibility and pricing

The iSpO2 connects via the old 30-pin connectors. If you own a newer iOS device with Apple's new Lightning connector (iPhone 5, iPad mini, etc.), you'll need to buy an adapter. I tested it on an iPhone 5 using Apple's Lightning to 30-pin adapter, and – as far as I could tell – it didn't affect the results.

If anything about iSpO2 will give you pause, it's the price. At US$250 (plus an extra $30 if you need a Lightning adapter), the iSpO2 isn't cheap. Especially considering that standalone oximeters with built-in displays can be had for less than $30.

Is it worth paying an extra $200+ for a) Masimo's measure-through motion technology, and b) the ability to sync with your iPhone? That's the question you'll need to ask yourself.

Summing up

Fortunately, pricing is about the only questionable thing about iSpO2. It's a simple accessory with a simple app that does one thing, and does it well. Few of us need to own a pulse oximeter, but for some, it's crucial. Perhaps, for them, the $250 price isn't so hard to swallow.

Masimo will be demonstrating the iSpO2 at CES 2013. It is currently available through Amazon, while the app is available as a free download from the App store.