Rohit from CloudMagic here. To build these 'additional functionality' on all platform, you need to roll out your own clients. We've started with the table stakes, stay tuned for those power features, across all devices. Extensions don't work on mobile devices and 70% of emailing is done on mobile today.
Surprised nobody has mentioned CloudMagic as an alternative to Greplin. Searches are much faster than Greplin and it has native Android Apps and extensions.