Online sensor data feeds, so you can experiment with other people's sensor data outputs:
Knoesis meteorological datasets (downloadable data)
datahub.io sensor datasets (downloadable data)
Safecast data API (api)
- Air quality in Scotland http://datahub.io/dataset/air_quality_in_scotland http://www.scottishairquality.co.uk/
Other places to look for sensor data: