iOS: Want to covertly check in on Instagram without opening the app? Feeday stuffs your Instagram feed right into your Notification Center.
Once you add Feeday to your Notification Center, you can just swipe down to see what's going on in Instagram. You can then tap a photo and head straight to the app. For free, you'll get the three most recent images, but you'll need to pay $1.29 for more images.
Feeday (free) [iTunes App Store]