I maintain a PPA package for numbat.
For that, I do something along this answer,
I ship the numbat binary for amd64 (from GitHub releases), and copy it to /usr/bin using the debian/install script. I also copy an icon and a .desktop file in a similar way, and package it using Launchpad recipe.
Is there any way to ship several binaries for different architectures in the repository, such that during building the .deb package, Launchpad will detect the architecture, and copy the appropriate binary to /usr/bin?