I'd like to announce an application called "Safe Arrival". In a nutshell, Safe Arrival allows one user to set a wakeup alarm on their phone, giving another user the authority to turn off that alarm before it sounds. Here are some scenarios where this might be useful, from the app description page:
Consider this scenario: Your teenage child is going out for the evening. As a responsible parent you feel you should wait up so that you know they arrived home safely. Using this application, however, you can be comfortable going to sleep, knowing that you will be woken up if your child is not home by a certain time. Here's how it works: You run the Safe Arrival application and create an "event". Creating an event is like setting an alarm clock. At the time you choose, an alarm will sound that will wake you up, UNLESS your child has arrived home and indicated that your alarm can be safely turned off. So if your child arrives home safely, you sleep through the night. Otherwise you are woken up by the alarm to investigate their whereabouts. If your child has the Safe Arrival application on their phone as well, they can use it to turn off your alarm. If not, they can send a normal text message to your phone, using a special syntax, that will turn off your alarm. That text message is intercepted by the Safe Arrival application so that it doesn't wake you up.
But the previous scenario only applies for children that have already earned a certain amount of trust. Sometimes a parent needs to enforce a curfew for a child that would rather stay out past the time they should be home. The Safe Arrival application is designed to help with this scenario as well. It works just as described above, with one difference: Your child must enter a password in order to turn off your alarm. Don't tell your child what the password is before they leave the house. Once they've left, write the password down and leave it at some agreed-upon place in the house. When your child gets home, they see the password and enter it into the Safe Arrival application on their phone, or include it in the text message they send to turn off your alarm. If they're not home in time, they can't turn off your alarm, because they don't yet know the password. In this manner, you can be assured that they actually arrived home. This is a limited form of parental control, and offers you a measure of assurance without having to watch your loved one at all times.
What if you're working while your child is returning home from school by themselves? You want to make sure your child makes it home as expected, right? You could set a repeating alarm or notification to sound at the time they should be home. When your loved one arrives home, they use their phone to turn off your alarm. If all goes well, you work through the day without ever worrying about it. If they are delayed arriving home for some reason, your alarm or notification sounds and you can call them.
A user of this application is either a "worrier" or a "traveler". The worrier is the person waiting at home, while the traveler is the person making the trip or outing. The worrier must have the Safe Arrival application installed on their phone. The traveler will find using the application to be very convenient as well, but it's not necessary for them to have it installed, so long as they can send and receive text messages with their phone. If both the worrier and traveler have the application installed, information is exchanged between the applications using text messages.
Scan this to get it from the Android Market: