If you're going on a solo trip or even for a walk at night, it's a good idea to let a loved one know you're safe. Kitestring is a simple webapp that checks up on you and sends a text message to your emergency contacts if you don't respond by a designated time.
Enter your estimated time of arrival and Kitestring will send you a text message to reply to. You can extend your check in time via SMS or check in early. If you don't respond to Kitestring's text message, your emergency contact(s) will receive your customisable alert message.
The free and open source site offers peace of mind, especially for those adventurous types and their families and friends. Instead of having to check up on each other just to say "I made it safe", Kitestring does the checking up for you. Although US-based, the service operates worldwide, including Australia.