- Firefox Nightly for Android installed on a device
- xpinstall.signatures.required preference set to false in said Nightly's about:config page
- The adb tool from Google's Android SDK
- Edit bootstrap.js to add/enable/disable debug code that gets injected.
- Create a zip file (with an .xpi extension)
- Push it to the device using adb
- Also push a html page that contains a link to the addon (as a security precaution, Firefox on Android requires a user gesture to install an addon.)
- Open the install.html page in Firefox Nightly
- Tap the link. You should now be asked if you really want to install the addon.
(The build / install.bat script will automate steps 2-5 above - until the "tap the link" part.)
When updating the addon with new debug code, you should probably go to about:addons on the device to remove the old version. Also, unless you're very carefully undoing all the addon does in an uninstall handler, it may be a good idea to also restart Firefox Nightly before re-installing the addon.