I've been looking around when I get a chance, The circuit to press the button should be similar to a circuit for a variable wiper. Instead of a wiper motor its a switch it activates intead.
http://www.techlib.com/files/wiperkik.pdfThe pdf shows a circuit for the wiper and should be easily made into system, get a vairiable dial with a on and off switch built in to deactivate the circuit, and since the original button can be left in place, that will function normally as well.
No while I've got variable intermitant wipers going, I found this.
http://www.miata.net/garage/int_wiper/index.htmlHe takes a miata control stalk and puts a variable resistor in it to make it well, variable. Our scion should have the same fixed resistor speed, and should be easy to make the mod. Anyone have the tech/svc manuals that can make a scan of the pages needed?
Now the rear wiper could also use it but a ready made cicuit is here
http://store.qkits.com/moreinfo.cfm?Product_ID=398&CFID=4561110&CFTOKEN=41371946got to head to work now.