I just got the Triggertrap cable dongle for my 5D Miii today for Christmas.
I downloaded the app to an iPhone 4s. Definitely simple to use to perform the essential operations. I tried out the cable release, magnetic trigger, seismic trigger, sound trigger and time lapse. All work essentially as expected, though with some caveats indicated below.
Word of warning...I have a tendency to jump in and experiment when I should be reading the info on the web and all of the help screens in the app that would likely have prevented many false starts.
My first impression in using the app is that there is a very long delay between the trigger event (sound or vibration) to the shot being taken. I took a closer look at the app and found that there are configuration parameters to control this.
There's a "Delay before trigger" which does what it sounds like. It creates a delay between the event and the activation of the shutter.
I was also finding that the camera was taking multiple shots on what I thought was one event. It turns out that there's a "Delay after trigger" that needs to be increased to prevent these multiple shots.
My app presets were: Delay before trigger = 850 ms. The in-app help said it should default to 0. Delay after trigger was set to 300 ms which is very short.
It turns out that these settings are forced when you pick "Canon Auto Focus" as a preset. So the app is working correctly.
So I tried reducing the delay before to 0 and the delay after to 3 sec. It's VERY hard to set accurately with the slider, so it would be nice if the app allowed direct entry via keyboard as well.
I soon realized that if I want to get a quick shot following a trigger, I need to be in manual focus mode. That's pretty obvious and it is indicated in the preset screen. So now I switched to the "Canon Manual Focus" setting. Sure enough, the delay before trigger is now 0 as expected. Delay after was still very low, so I just increased that setting.
As a test, I dropped a soft, spongy rubber ball onto the iPhone when seismic trigger was set. I got one shot when I dropped the ball. The shot occurs after the ball has rebounded about 18 inches. So it's not useful to record the actual impact.
In summary, I would say this is a very cool tool. I got the app for free and the dongle was a gift, so the price was certainly right! I look forward to trying a serious experiment with it.
By the way, the magnetic release was really cool. I was able to wave a magnet over the phone to trigger the shutter. I can imagine sneaky ways to use this to automatically trigger when a door or window opens, but it would require a MUCH longer cable to connect the phone to the camera. I guess this is where the WiFi slave mode would be useful.
Here's a link to a YouTube review: http://www.youtube.com/watch?v=Qxu2yEu6dSY