It’s the beginning of the holiday season and that means one thing: Toys! Here are some of our favorite new digital gadgets to help you do right by Mother E.

 greenMeter

Remember when the first carbon footprint calculators started coming out about two years ago? They were pretty clunky, giving you only a rough idea of how many planets humanity would need if everyone on earth lived like you did.

Like everything in this space, the tools are only getting more sophisticated by the day. To wit, the smart folks at Hunter Research and Technology have just released greenMeter, an app for your iPhone or iPod Touch that uses the devices’ internal accelerometers (didn’t know they had them, did you?) to calculate your vehicle’s fuel efficiency, carbon footprint, and even how many barrels of oil you’re consuming. The app will be most useful for hypermilers, those hobbyists trying their darnedest to squeeze every last ounce of fuel efficiency out of their rides. But at $6 a pop (via the App Store in iTunes), it’s not a bad feedback system for the rest of us.

Botanicalls DIY Plant Twitter Kit

Earlier this year, my grandmother asked me what kind of flowers I wanted for my birthday: Cut, or plants?

“Cut,” I answered. “That way I can’t do them any more damage.”

If you’re like me, not only do you have the brownest of brown thumbs, but you honestly couldn’t interpret the signals a plant was trying to send you if your life — or, more accurately, its — depended on it. Which is why any system designed to let me know when a plant needs watering seems like such a brilliant idea. First there were the manual moisture meters that you stuck into a plant’s soil, thermometer-style, and read the dial to see how dry it was. Then came the handy sensors you left in the pot at all times so they could light up when your little green buddy needed a drink.

Now, for the always-connected set, there’s the Botanicalls DIY Plant Twitter Kit — a sensor left standing in your plant’s pot that will send you a Twitter message the instant your plant starts feeling parched. At nearly $100 a pop, it’s only for those still feeling flush after the economic downturn. But I like where this thinking is going.

WeatherTRAK

Most pre-programmed lawn-watering systems rely on the user to make a decision about when their greenery will need moisture, and then off it goes, irrespective of what the weather actually does. Which means some lawns get too little water (when the irrigation system lies dormant during unusually dry periods) or, more often, too much water (when the irrigation system turns on as programmed during a rain storm).

WeatherTRAK solves that problem by wirelessly plugging into 40,000 weather stations and satellites around the country to determine exactly how much water your landscaping needs and then automatically turn your sprinklers on and off as necessary.

HydroPoint, the company that makes WeatherTRAK, estimates that most lawns and gardens are over watered somewhere between 30 to 300 percent. In comparison, the company’s 15,000 subscribers ended up saving 6.7 billion gallons of water last year — and $60 million. Now that’s the kind of green we like.