One of our more interesting finds at last night’s gdgt live Seattle event was a service called ‘Cloak’ that protects Mac, iPhone and iPad users from having their data intercepted when using unsecure web sites over public WiFi networks such as those in many coffee shops.

It’s developed by a Seattle startup founded by a trio of Microsoft veterans: engineers Dave Peck and Peter Sagerson; and product designer Nick Robinson. The service is currently in public beta, building up to a larger launch, but the startup is already profitable, Peck told us last night.

How do they make money? Cloak is free to use for up to two hours of usage and 1GB of secure data transfer a month. Beyond that, subscription plans are available for $8/month for up to 20GB of data, and $15/month for 50GB, without time limits — targeted at people who spend a ton of time at coffee shops or on other public networks.

The technology is a VPN, or Virtual Private Network, but as demonstrated in the video above, it’s designed to be simple to use, sensing when someone is on an unsecured network and automatically turning on behind the scenes to protect the data they’re sending.

Why would someone need this? Peck cited the example of the hacker tool called Firesheep, a demonstration created by another Seattle developer, Eric Butler, to show how easy it is to collect personal data from people on public networks.

“It’s really scary,” Peck says. “Cloak is sort of the antidote to Firesheep.”

Why Mac and iOS? Despite working at Microsoft in the past, the team has experience in the Apple ecosystem. Sagerson, for example, was an engineer in Microsoft’s Mac Business Unit, involved in areas including security for Mac Office.

Peck explains, “We started with the Apple ecosystem because it’s one we know very well, but we’re excited to start supporting Android and Windows just as soon as we can.”

The iOS app is available here.

(Post updated to correct the respective roles of the three founders.)

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