Another plus of the BART Widget is that it's open source; Victor invites anyone making their own trip-planning widget to use his code to jump-start theirs.
And finally, it's free, but if you want to show the programmer some love and thanks for keying in that mountain of schedule data, buy one of his CafePress swag. (Though it pains us to say it, while the BART Widget itself is cute, the t-shirts are, well, kinda turdy.)