Yes. Mailtrack has a standalone app for both iPhone and Android. You can download it now:
iPhone and iPad — Download on the App Store
Android — Get it on Google Play
In the store, look for Mailtrack® published by Mailsuite.
Sign in with the Google account you already use with Mailtrack, and every email you send from the app is tracked automatically — no setup per message. You get a push notification the moment someone opens it.
The app works on phones and on tablets, including iPad.
Would you rather keep writing from Gmail?
You can also add Mailtrack to the official Gmail app with the Gmail add-on. It's a lighter option: you turn tracking on message by message, and it doesn't run on tablets.
Mailtrack for iPhone and Android compares both and walks you through either one.