I have never specifically used options to tie up real estate, but have traded stock options and thought I would throw in my .02 cents on risk.
Any option is simply a contract between two parties where one party pays a monetary amount up front (premium) for the right, but not the obligation, to purchase some asset at a set price over a specified time frame.
I would assume you could hire a lawyer to structure the terms of this option contract to meet your specific needs (the size of premium you would offer, the selling price of the land, the time frame that the option was good for). The longer the time frame, the higher the premium will most likely have to be to entice the seller to enter into the deal.
The big risk with any "derivative" instrument (options, futures, etc.) is that things may not go like you planned over the time frame that the option covers (development goes slower than planned, you can't find a buyer, etc.). If that happens, the other party keeps the option premium you paid them and keeps their land also.
Remember, with any "derivative" instrument, you are using an incredible amount of leverage, but time is your enemy. You have to be "right" twice. The value of the land has to go up AND it has to go up within the time frame your option covers.
Hope that helps a little bit!