In the world of computer networking, a "ping" is a cry into the darkness "hey, is anybody out there?" Technically, ICMP "echo request" packets are sent to another machine on the network, and then you wait for a corresponding ICMP "echo response" to come back. In the real world, when you "ping" somebody, you're just briefly touching base with them, seeing if they're there.
Pinger takes this "ping" to a new level. With Pinger, you can leave voicemail messages for your friends, and they in turn get a text message telling them that you called. They can then listen to the voicemail message on their schedule. It's more personal then a straight-up text message, but it's not as intrusive as getting that phone call at 3:00 am. Are you four hours ahead or behind me—I can never remember. Where your text message is limited to only 160 characters, you've got a good five minutes of voice message available. You can send your message to groups of contacts as well, so you can get the word out to everybody all at once, rather than having to leave a hundred voice messages.
How much would you expect to pay for all this? $50 a month? $5 a message? Wrong-o, SMS Breath, it's absolutely free. Well, regular air time and text messaging rates apply, but the service is free. It's available in the US and Canada, as well as several other countries in Europe, Latin America, and the Pacific Rim as well.
You can use Pinger by just sending a message. In the US, dial 858 2 PINGER (1-858-274-6437), or you can sign-up online at the Pinger website, which gives you access to more options, like an editable contact list, in-box browser, and other tools.