[Vlad-Andre] used some of his free time to build an alti-variometer. He does some para-gliding near restricted air space and wanted a backup altitude warning that would help keep him below the mandated altitude. His solution uses the SparkFun Weather Board in conjunction with their BlueSMiRF dongle to measure altitude and transmit it via Bluetooth. From there, he wrote a program to grab the transmitted data with his cell phone and display the information. His application also has the ability to set altitude warnings and log changes over time.

Using this system he is able to get altitude data with 3.5 inch accuracy. Because the capture application is written in Java it should be easy enough to make this work on other cell phone models. The project is clean and works well but we estimate the cost of the parts to be between $250-300, making it out of reach for those who don’t have a specific need for these types of measurements. This is especially true for paragliders who have much less expensive options available to them.
[Thanks Carl-Emil]

[Matthias] from Intuity Media Lab put together a nice bit on controlling office lights with XMPP from his Android phone. In the article, he explains the components involved in the project, why he chose XMPP, and lists everything you need to replicate it. The project makes use of a wide variety of tools and libraries, weaving together code from multiple languages to achieve its goal. Overall, his project is a welcome change in a world full of Twitter-based solutions.

Here’s a quick prototype from [Travis Goodspeed]. It’s a smart card built around an MSP430 microcontroller. We’ve used the MSP430 in the past because of its low power demands. He says this business card currently supports 1.8V to 3.3V, but a future design will have 5V as well. Technologies like Java Card exist for running applets on smart cards, but a familiar microcontroller like the MSP430 could certainly make development much faster. Knowing [Travis], there’s a reader somewhere about to go through some serious fuzzing.

We’ve heard about the idea of using browsers as distributed computing nodes for a couple years now. It’s only recently, with the race towards faster JavaScript engines in browsers like Chrome that this idea seems useful. [Antimatter15] did a proof of concept JavaScript implementation for reversing hashes. Plura Processing uses a Java applet to do distributed processing. Today, [Ilya Grigorik] posted an example using MapReduce in JavaScript. Google’s MapReduce is designed to support large dataset processing across computing clusters. It’s well suited for situations where computing nodes could go offline randomly (i.e. a browser navigates away from your site). He included a JavaScript snippet and a job server in Ruby. It will be interesting to see if someone comes up with a good use for this; you still need to convince people to keep your page open in the browser though. We’re just saying: try to act surprised when you realize Hack a Day is inexplicably making your processor spike…

[via Slashdot]

When we first saw [Jeffrey Nelson]’s G1 based robot we immediately wondered what the transport for the controls was. The G1’s hardware supports USB On-The-Go, but it’s not implemented in Android yet. It turns out he’s actually sending commands by using DTMF tones through the headphone adapter. The audio jack is connected to a DTMF decoder that sends signals to the bot’s Arduino. He wrote client/server code in Java to issue commands to the robot. You can find that code plus a simple schematic on his site. A video of the bot is embedded below.

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[Josh] sent in a home automation project he did a little while ago. It has a total of eight switched outlets. The main focus of the project was WAP access for remote control from any cellphone. The control box is based on a design by [Ashley Roll] for controlling eight servos using a PIC microcontroller. A listener app written in Java monitors the control web page and sends signals to the board via serial port. He used opto-isolated 240V solid state relays for each of the outlets. All the pieces are available on the site and he might even do a custom control board design if there is enough interest.