How do I display a View Chart on the Dashboard?

Sometimes a good old "oscilloscope" time series chart is all you want

The View page is for inspecting individual devices one by one, including showing their current properties and how they have changed over time. The Dashboard page is for showing metrics on lots of devices. If you are at trial stage with only a small number of devices, or you have a particular device that needs special attention to (e.g. a VIP device or a problematic device), then you might want to display individual device data on a Dashboard. 
e.g. to plot historical chart data from a few individual devices on the Dashboard, define a KPI that is grouped-by device:
1) Go to the Cohort page
2) Set the Metric to "Mean value of" and choose the property you want to plot
3) Group by $id (so that every device is shown as a separate trace)
4) Group by Time 15m or even 1m (to give you a high-resolution oscilloscope trace over time)
5) Set the time period at the top to however long you want, e.g. 7 days
6) Optionally, create a Scope filter to choose just the devices you're interested in (if you want just one device, then create a filter where "$id is equal to X").
Once you've done that, save the KPI with a meaningful name. Then go to the Dashboard, unlock it, Add Widget/KPI, choose your KPI and voila!
individual device chart