A "keyboard attachment" refers to a device or accessory that can be connected to a computer or other electronic device to provide a physical keyboard for typing. Full definition
You can buy good keyboard attachments for them both. (digitaltrends.com)
For those who want to be more productive, there's an optional keyboard attachment that will make typing a much more productive activity. (ubergizmo.com)
The larger display would support larger Bluetooth keyboard attachments, for starters. (gigaom.com)