[Tinyos-help] gas sensor and bio-sensor

[Andy]

Hi,

I am wondering whether there are gas and bio-sensors (compatible  with 
research platforms from xbow, moteiv etc.) available. It seems the 
current popular sensors are light, temperature, humidity, vibration, 
acoustic, accelerator, etc. The chemical and bio-sensors seems not 
popular but they are also very useful. Any information, links, documents 
are appreciated. Thanks a lot.

Regards,
Andy