What does this $249 option get you? Does the model #3 come with any security system at all? Do all models have keyless entry? Still unclear to me even though I've spent some time checking the Toyota web site and other sources.
Because there is no "key" for the car now, it is probably more secure since it's harder to bypass.
Whether or not you need additonal security for the car would depend on where you live. If you know of a lot of other car thefts in your area, I would probably go for a system, if only to get lower insurance rates (it probably pays for itself in the long run).
If you're thinking about model #3, I strongly suggest #6, which is the same only with Smart Start/Entry. I'm really in love with this feature (I originally thought #3 was enough for me). I'll probably never get to use the airbags, so may as well get something you'll use every day!