I just want to let everyone know that the Tizmos Start Page CAN two switch scan. It is far from perfect, but you can use the tab to move through all selectable objects on a page one at a time and enter to select one. Thus a switch set to "tab" and another to "enter" will do that same thing.
A tip is to use some of the accessibility features in your operating system and browsers to make what is being highlighted as you "tab"/scan through the options more obvious. Another tip for scanning is to be sure the link on Tizmos goes directly to a switch accessible page and not to a non-accessible entry page.
Note: this isn't going to work perfectly because some pages that are linked to need different switch settings (i.e. space bar not enter) or there is no way to link past the set up page effectively. Someone will need to be on standby to help.
Maybe someone can let me know a way to refine this or Tizmos or another start site would be interested in adding single switch scanning or more refined step scanning.
You can try my Tizmos Launch Page here or make your own.