For a mere $100 per house plant, you can purchase theBotanicals DIY Plant Twitter Kit . Then, you can spend at least a few hours to put it together -if you even own a soldering iron to start with. Assuming you can actually put the piece together and set up the Twitter feed for your plant, you should then be able to subscribe to the plant's feed and follow your plant's thoughts.
Fortunately (at least according to the Plant Twitter Kit), all that plants think about is water. Your plant's Twitter feed will essentially complain to you if you have over watered it or beg you for more water if it is hungry. It occurs to me that perhaps a better solution would be to install legs on your plant's pot and let it walk to the sink and water itself. All this dependency is really just pathetic.
Regardless, this invention still is pretty cool. I do have to wonder if it will be accurate for all plant species. Obviously orchids require more water than cacti, and who knows if there's a way to program the kit to recognize this. Those things taken into consideration, I've gotta say, it sounds like my houseplants have a much greener future to look forward to.
You can get this at ThinkGeek.com