Something that makes SmugMug an excellent Instagram alternative is the ability to download entire galleries so they’re available offline for when your signal isn’t the strongest. This can be a lifesaver, especially if you’re using your account as a professional photographer. You can also share images directly from the app via SMS, email and social media, so it’s not limited to face-to-face sharing.
The aptly named Hipster borrows a lot from Instagram, including the snappy photo shooting and all of the great filters you can apply to your photos. Hipster also allows you to add text captions to your photo "postcards" before sharing them, and then post your photos to Twiter, Facebook, Flickr, or Tumblr for others to see. It's fast, easy to use, and probably the simplest to get started with in the roundup.
A simple chat (slack style) it's enough. Just having the possibility to send messages either single user or team (#channel). But please don't forgive to give an useful appeal to mobile app (worst error of competitors is, have a good app but totally no mobile friendly!) i would expect to have a similar whatsapp or slack app for messaging within the slack mobile app!