Cool!! Remotely accessible sensor for managing irrigation and other stuff. The device is sold by a Switzerland-based company called Koubachi. Too expensive for house plants but could be great for agricultural applications. http://allthingsd.com/20130613/high-tech-help-for-the-green-thumb-challenged/.
The review focuses on the remote (mobile) accessibility of the device, which is amazing, but doesn’t talk at all about how accurate the internal sensors are. If anyone has this information please leave a comment. I also will try to check on this.
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PRAGWATER 
A major drawback of a product like this is that is gives you information like: “needs water now”. But it doesn’t tell you how much water to apply. This is the biggest problem in irrigation management. For more information, download my recent presentation on this topic: http://academic.uprm.edu/hdc/documents/An%20Agricultural%20Application%20of%20GOES-PRWEB,%20presented%20at%20NOAA%20CREST%20symposium,%20NYC,%20%20June%206,%202013.pdf
Apparently the Pro version of the software does provide additional information. The image at the following link shows that it will provide soil moisture tension, temperature (soil I assume) and solar radiation (in Lux units). http://www.koubachi.com/news?locale=en
Correction to previous comment. I said “solar radiation (in Lux units)”. Lux are units of solar illumination and not power. According to wikipedia:
“There is no single conversion factor between lx and W/m2; there is a different conversion factor for every wavelength, and it is not possible to make a conversion unless one knows the spectral composition of the light. (https://en.wikipedia.org/wiki/Lux)
Hi there! Thank you for the comments! Once you set the plant we do give also detailed instruction about how to water the plant, how much and if some special care is needed (for e.g. use of rain water only). These information are visible if you tap on the water icon in the care view.