You can build your own cross platform chat app similar to Slack or FB chat. iFlyChat REST API's are currently popular on web & Mobile. It is quite affordable entreprise chat backend solution. iFlychat API can be integrated on web as JS/Plugin and SDK on Mobile. Platform and stacks: Drupal, Wordpress, Php, Perl, iOS and Android.
You can build your own cross platform chat app similar to Slack. iFlyChat API's are currently popular on web but has a potential to become Akamai for Chat app aka CDN (Chat Distribution Network). iFlychat API can be integrated on web as JS/Plugin and SDK on Mobile. Currently it is popular in Drupal, php
