Prior to purchasing a dedicated shot timer I took a look around the Apple app store and found Surefire’s shot timer application, called simply “Shot Timer”. It was and is still free and is arguably more polished than many commercial applications. The basic functions of generating a starting sound and timing subsequent shots is done nicely. The only problems I have ever encountered were 1) the starting beep isn’t terribly loud (tough if you don’t have amplified earmuffs) and 2) the sensitivity adjustments are a little challenging. Once dialed in the system works quite well. The trick seems to be to find the precise spot where your shots are detected but spurious signals are ignored. For example, I have noticed that when sensitivity is slightly low, not all shots are detected. Likewise, when too high it picks up shots from other nearby shooters (even on adjacent ranges). Nevertheless with some work this can be overcome .
So, is this a viable alternative to hardware shot timers? I don’t think so. The CED 7000 is far superior in terms of sensitivity (I’ve never adjusted it from factory defaults) and it is simpler to operate via its physical buttons. However I have returned to using Shot Timer for practice in certain conditions. Specifically Shot Timer gives you complete results of every shot and split time in a beautiful list right there in front of you after shooting is complete. Yes, all the same data is available with traditional shot timers, but only by scrolling through the shots sequentially, which doesn’t allow at-a-glance comparisons of splits and transitions. The result is that you can now shoot a stage and instantly see what is taking the most time: splits on the same target, transitions, movement and/or mag changes. Most folks probably look at the overall time for a stage and don’t really consider what costs what. With Shot Timer you can see exactly where time is going and subsequently work on those areas that are costing too much. I notice that on stages 
with close targets my on-target splits are around .25-.35 seconds, transitions are .45-.55 seconds and mag changes are around 1.5-1.75 seconds. Your mileage may vary of course. Seeing all this data makes it easy to focus on a particular aspect of your runs, say splits, and see the results in both time and accuracy. Try once fast then slow and compare the two runs. This is an invaluable way to determine which direction your training should take.
One other big advantage to this app is that you can email the results for each run. This is a nice touch as it allows you to keep an ongoing record or just spot check occasionally.
So why does Surefire give this app away? I don’t really know. My guess is that they like the PR and brand promotion and the app likely cost them very little to produce. In any case it is a great tool if you can’t afford a hardware timer and as shown here, it has some unique benefits too.
Firearms4u 