When you’re away from home and your cellphone runs out of juice it can be a real downer. Sure, you could find a store and buy a wall charger, but wouldn’t it be more fun to build your own battery booster without using tools? [Spiritplumber] did just that, popping into a Radio Shack for the parts, then making his how-to video (embedded after the break) while standing at the checkout counter. You can see he hust set his camera on top of the battery display case and got to work.

He’s using four D cell batteries to provide 6 volts of power. Assuming your phone charges at 5 volts this is going to be just a bit too high, even though there’s some tolerance with most phones. To overcome that obstacle he added a diode to the circuit, taking advantage of the 0.7 volt drop that it brings to the mix. Grab a plug adapter for your model and then just hand twist the connections. [Spiritplumber] admits it would be better to solder these, but in a bind you can get away with it. We looked up some prices for this method and we figure this would cost around $18 (batteries included) depending on the price of the plug adapter for your phone.

Of course if you’re just looking for a way to charge your phone without paying consumer prices there are ways of accomplishing that as well.

[Thanks Mkb]

[Tim] is showing off the first step in his home automation projected with this smart-phone garage door interface. In the video after the break you can see him open and close the garage door with the touch of a button. There’s also an open or closed indicator that he can check when away from home.

An Arduino takes care of a portion of the control for this project. Like the post we saw yesterday, he’s using PHP code on a webpage to manipulate the Arduino via its USB connection in order to open and close the door using a relay. The door status is also monitored by the Arduino and sent to the PC over the serial connection. The computer uses a Python script to monitor the incoming data and update a text file which is merged into the web interface using a PHP include. Future plans for the system include adding control for heating and air conditioning systems.

If you’re looking to do something like this but wirelessly here’s some advice on ditching the Arduino and using an XBee module instead.

Idle developers of the world take inspiration from this project and unite to create your own version. It’s called the Junkyard Jumbotron because it takes many different displays and allows them to be used as one big interactive display. The image above shows a collection of smartphones displaying a test pattern. The pattern is unique for each device and is used to calibrate the display. Using a digital camera, a picture of these test patterns is snapped, then sent to the server. The server calculates the position of each of the screens, then sends the correct slice of a large image back to each phone.

It’s funny that they use the word Junkyard in the name of the software. Each display needs to be able to run a web browser so you can’t just use junk displays. But one nice side effect of the hardware requirements is that you can still do things like panning and zooming as seen in the video after the break. Here’s the real question: can you make this work as an open source project? How about something that can be easily set up to work with a LAMP server?

[via Reddit]

Our friend [Jeffrey Sharkey] hacked the iTunes remote control protocol and produced his own version for Android, one of the smartphone OSes we just covered. He pored over dumped packets for a few days and wrote a client which is of course GPL’d. Besides that, he’s been busy winning the Android Developer Challenge. His app, Compare Everywhere, was one of the top 10 winners, netting him a cool $275,000. This ingenious bit of code deciphers barcodes scanned using a cell phone camera and then finds prices for that item at every nearby store that sells it.

The other winners wrote apps that do cool things such as one-click cab ordering, locate missing children, and find parties. Check out all 50 finalists and winners here.