How close to the iMac must you be to use your iPhone or iPad as a remote? I often present 10 or more miles away. Can I play my Keynote show remotely from my 27" iMac?

I am discovering the wonders of an iMac and am both surprised and delighted at its capabilities. However, I can't figure out from the comment threads on Keynote '09 how far away from the iMac I can be and still access it using my iPhone or iPad as a remote? If you've booted up your iMac to the page your slide show is, can you be presenting 5 or even 20 miles away? Can I put the Keynote presentation on my iPad and play it on a monitor furnished by place where I'm giving the speech? Will it be as crisp a display when beamed from my iPad?

Alternatively, can I put the Keynote show onto a thumb drive, connect that to my host's computer, and then play Keynote?

Also, do you need iWork to use Keynote? It's not clear from the description.