Checkmark has been described as the pro version of Apple's included Reminders app. It's on sale for $0.99 for today only.
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Since it's only available at $0.99 for today, I thought I'd post a quick gallery of screenshots of the initial setup of Checkmark which should show you a lot of the care that went into making this app. After I've played with it for a while I'll post a more thorough review.
My initial impression is that it's a great looking app with lots of little touches (like the ability to set the range for how far from your location the app's "radar" should alert you) and better usability than Apple's own Reminders.app included in iOS5.
Gallery of Initial Usage permalink
Click on the first image and scroll through to see the procedure of setting up Checkmark for the first time, adding a few locations and adding a location-based reminder. 1
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Get it today before it goes up in price: Canadian App Store / US App Store