I'd avoid wireless unless you have some odd circumstance that demands it.. More batteries + interference problems = hassle that for most people outweighs the benefit of running all of 12 inches of wire.

My favorite is the Sigma BC-1600 as well, it can be acquired for around 20$ if you look on ebay, and slightly more elsewhere (though still quite reasonable, even at its MSRP), it holds two wheel sizes in memory (for switching between two bikes, if you buy a second sensor assembly), has about every feature you'd want, including an optional cadence sensor, intelligent controls, good size, and flexible mounting options (mine is mounted on my stem).

Oh, and it took me about 15 minutes to cleanly install...

peace,
sam