"add on option" is a valid expression in written English.
You use it when you are introducing an additional, optional feature that is available to a user. For example, "We are now offering an add-on option to our basic product package that includes additional customer support."
I chose a few add on options for my bag, including a shoulder strap, front pocket, and a USB key holder.
Then realising that it depends much more on Flash technology I added it to Flashblocks 'white list (Tools - Add Ons - Flashblock - Options - add www.bbc.co.uk to the white list).
There was also some confusion when it came to the "add-on" option for services on a user's service list, so there is now a tooltip for that as well.
Blindspot monitoring with cross traffic alert is also available as an extra add-on option.
Pedestrian routes have only been considered as an add-on option in existing digital maps and the respective data collection has not been performed in the field.
There's also a brand new stainless-steel rotisserie kit add-on option, complete with cordless battery, for $249 that adds yet another level of open fire cooking capability, but I haven't tried that yet - maybe next year.
Another add-on option would be limiting the total amount of downloads to increase demand and/or waiving the viewing constraint to launch a more focused drive in traffic.
Flux's modular units allow it to become a 3D scanner, later engraver, ceramics or pastry printer using modules either included, available as a separate add-on option or in development for later release.
The integration works through the iPhone's lightning port, meaning that it's only compatible with iPhone 5, iPhone 5s and iPhone 5c, and of course not ever new car sold will have CarPlay integration built-in (it'll likely be an add-on option for many of these manufacturers, since it represents a chance to offer additional value and that's generally the way upgrade packages work).
The source said something jokingly about how it's really a re-designed version of Vista, and, to their surprise, the PR type said, "No, Vista runs great on the new Macs by itself, and Bootcamp 2 lets us ship it as an add-on option for dual-boot".
Standing in solidarity for the unwarranted loss of life doesn't come with a simple clickable add-on option on Facebook.
