I believe there is already an outstanding request to include temperature (from a Tempe ANT+ sensor) - I would like to add my vote for this, and also to make the on-device temperature available in case a Tempe is not present.
Additionally I would also like access to the atmospheric pressure in hPa. Both of these are available in Sensor.info, but of course that's not available to DataFields.
Knowing temperature & pressure would allow a DataField to make a pretty good estimate of air density, which would be useful for all sorts of aerodynamic and virtual-power goodness in a cycling scenario.
Thanks in advance,
Darren