Good wireless.. Yes.. The '03 Cateye wireless is a good one, and goes for about $60. The '02 model was more expensive, but if you can find one you may get a deal on it.. As far as weather proof? Most are.... In fact I have yet to find one that isn't. Thermometer? Yep.. Cateye also makes one that has a thermometer in it. Also has a barametric altimeter in it. I used one for about a year, and when I replaced my bike I replaced it as well.. It works fine, but living in the Seattle area, our barametric pressure changes every few minutes I think.. And I wanted a wireless.. It retailed for about $100. If you are interested in it, I'll sell it to you for $50. I have all the paperwork and the box..
I think about the only thing you may get for under $30 in the cycling world is advise... Happy riding.