It depends. How many did you plan on buying?

It's your privilege to "pull apart" the app, if you think it deserves that. I was just trying to explain why the issues you brought up aren't a problem. I'm more interested to know if you bought one! :-)

iHolophyte: You've missed a couple of important points. The speed you set is just a minimum speed which arms the app when you are driving above that speed. You can set it at 10 MPH and leave it there. If you are driving normally (and safely), decelerating from whatever speed you are driving...

Don't forget to drive safely while you're checking! :-)

Darkstar: You are 100 % correct. It emits an audible alarm so that you know (if you are conscious) that it is about to send the messages it has been programmed to send.

If you drop it at home, it will not activate. If you drop it in the car, while you are driving faster than the activation speed, it MAY activate. If it activates, you always have 60 seconds to deactivate it.

Isn't it time to check out MayDay, the only iPhone app which can save your life? This is not an app which can provide instant gratification. It is not a game. It won't help you find a restaurant. It won't help you pass the time on a train. All it can do is save your life. Think about it...

BAB2010: OKMURDOG is right. The program will not activate every time you stop at a red light. It only operates if you are driving above a preset speed (which you set) and you suddenly stop, or are stopped. You (or the car) have to go through a serious deceleration for the app to operate and...

The iPhone has on-board accelerometers and a speed detector for the GPS. Using the speed detector, Mayday knows that you are moving. It then uses the accelerometers to detect a sudden decrease in speed which is a very good indicator of an accident. It then sends a message to whomever you...

Check out was was just written about Mayday on iPhone Life online magazine: http://www.iphonelife.com/issues/2011Sept-October/FacingACrisis The article only mentions Mayday Light, but Mayday Pro is far more powerful.

An answer to TRJeff: It can call 911, but it can't talk to the person who answers. If the police have an sms number or an email address, it could send a message there....

SWEARPORT: What exactly does your post mean?

A few years ago, the developer passed a car accident on the road. He saw that the police were already there, so he didn't stop. He only found out later in the day that his older brother had been involved in the accident. Had he known when he passed the accident, he could have stopped to help...

Don't forget that there are 2 versions - Mayday Light, and Mayday Pro. Mayday Light only sends email messages while Mayday Pro sends SMS messages as well. The Pro version is far more effective, although it's far better to drive carefully and avoid accidents. And of course, they both work.

Mayday is an application which definitely works. The iPhone has on-board accelerometers and a speed detector for the GPS. Using the speed detector, Mayday knows that you are moving. It then uses the accelerometers to detect a sudden decrease in speed which is a very good indicator of an accident.