I really like the sound of Nashville tuning, where you typically replace the EADG (low to high) strings with lower gauage strings to get a really light sparkly sound. Is there a way of emulating this sound without having to re-string my guitar every time I want to do it, using effects pedals?
The Roland VG pedal boards will change your guitar tuning to whatever your little heart desires. Joni Mitchell used to use one for her 50+ different guitar tunings. (Source: http://www.jonimitchell.com/library/view.cfm?id=38)
The Roland VGs require a GK hexaphonic pickup that picks up up each string separately.
More info here: http://www.rolandus.com/products/details/849/specs/
Any Line 6 'Variax' guitar can do this, & you can set up presets you can literally dial in from the guitar itself.
The initial programming needs the guitar to be connected via a specific hardware adapter [supplied as part of the new package] via USB to a computer [Mac or PC] - but the recall, once programmed, is straight from the guitar, so can be used live without a computer.
http://line6.com/guitars/ or find an old one in a second hand shop or eBay...
There are many different makes and models of polyphonic pitch-shifter effects pedals, but they will shift the pitch of every note you play on every string up or down by the same amount. That's not quite the same as Nashville tuning. Furthermore shifting the pitch of the strings by that large of a degree sounds quite artificial.
Go to your local music store and ask what models of polyphonic pitch shifters they sell, and ask to try them out.