Here is a short-list of missing features for international mobile users. Feel free to contact me on @msuiche or over e-mail if there is any feature you think is missing but more necessary than changing the colors of your icons at every release.
1. Smart address book
There is no reason your contact book would not allow you to automatically sort your contacts out per country using the Prefix Country Code, nor per city or region using the prefix following the country code.
Moreover, a map-based browsing would be more intuitive for its users – as per example the illustrative screenshot below.
And also timestamps your contacts to provide better triage mechanism based on time / day / month / year.
2. Smart international keyboard
There is no reason Messaging application could not remember what keyboard layout I use for different contacts. If you message different people using multiple languages, your app should at least remember your preferred keyboard layout per contact.
3. The end of the single number identity
There is no reason applications would tie your identity to a single number. Applications such as messaging applications (WhatsApp, etc.), food delivery applications, or even car booking applications (Uber etc.) only allow their users to have one single number. Users should have the ability to have multiple verified numbers, people who travel usually have one number per country.