The Samsung Galaxy S5 smartphone is unique in that it features\u00a0a heart rate monitor built into the device itself. It is operated\u00a0by simply placing your finger over a special part of the phone and waiting a few seconds. But how does it work, and how does it compare with what's already available on the iPhone?How they workThe Samsung Galaxy S5The new heart rate sensor is found on the back of the SGS5 just beneath the main rear-facing camera and works by firing a red light through your finger. From there it can capture your pulse so it knows how fast your heart is beating. This information is then shared with Samsung's S Health app.The iPhone 5SThere isn't a built-in heart monitor with the iPhone 5S, but you can download an app that will allow you to capture your heart rate in a similar way to the Samsung Galaxy S5.One of the better apps available is Instant Heart Rate, which works on the iPhone 4\/4S\/5 because it has flash, and on iPhone 3GS and iPod touch, but you have to use in good lighting. The app uses the iPhone's camera to analyse colour changes on the tip of your finger. Like the system in the SGS5 you are asked to place your finger on the camera lens for a few seconds so it completely covers the lens.SoftwareThe Samsung Galaxy S5Samsung has embedded the heart rate monitor feature into the S Health app already available for Samsung devices and will be the same on the SGS5, but with the new heart rate feature.Once captured you will be given your heart rate and that is added to a graph so you can plot your heart rate over time and these can then be viewed back in hours, days, or months.There doesn't seem to be any way to tell the app what you were doing, so you'll need to make sure you don't mistake a reading during exercise as the time when you almost had a heart attack. It also doesn't look like you can share the data out of the S Health app at the moment.The iPhone 5SBecause the iPhone doesn't come with a heath app of its own, you have to use third-party apps to access and record the information. In this case a dedicated app called Instant Heart Rate. It allows you to log your heart rate, tell the app what you were doing at the time (resting, exercise, standing, etc), and see trends over time. The app can also be integrated with other apps such as activity tracking app Argus that uses the iPhone's motion sensors to track how far you walk in a day or let you track how many calories you've burned.PerformanceThe Samsung Galaxy S5In our play at the Samsung Unpacked event in Barcelona, and again on the company's stand at the show, we tried the heart rate monitor several times with different people. On the whole grabbing our pulse from the device was very quick and very easy. Open the app, press the button, place your finger on the dedicated sensor, and seconds later you have an answer. We don't like that the data is only recorded to the S Health app rather than being available to third-party apps, although we should point out that this might change come launch day.The iPhone 5SThe Heart Rate app for the iPhone costs \u00a31.49 and although it works, it does take longer to lock down on your pulse. We've found in the numerous tests we've done that you have to be very still for it to work (the phone as well) and you then have to remember to clean your camera afterwards otherwise your pictures still have your mucky fingerprints on them.But we do like how you can tell the app what you were doing at the time of grabbing the information and that you can then share that with other apps that support the Heart Rate app.ConclusionIn reality both work well as each other, with the SGS5 allowing for a faster, cleaner capture of your heart rate, but the app for the iPhone allows you to do more with the end result. The good news for consumers is whether you choose the SGS5 or the iPhone 5S you'll be able to monitor your heart rate whatever the day or night without having to place your fingers into your neck and start staring at the seconds on your watch.