The latest version of inTextMoji app for iOS (formerly known as the EmojiXPress), includes a new way to send custom emojis inline with text, in all apps. Since the app works outside of Unicode emoji approvals, it’s able to include real people, logos, and other characters that might not otherwise be eligible for Unicode encoding (via Emojipedia).
Best of all, inTextMoji works system-wide so it doesn’t matter which app you use. The keyboard can show the options to insert, and the font does the rest. Once you download the app, you need to install the custom font via the app and then activate the custom emoji keyboard in Settings. Once the keyboard is enabled and the font is installed, access is via the input switcher, like any other third party keyboard.
At launch there are 187 custom emojis in the app. It’s likely that more will be added over time. Also, both sender and recipient need the font installed to see any of the custom emojis. You can download the inTextMoji app for iOS at this link.