@Adam.reber, as discussed, you can refer to my Splunk Wiki Talk topic for jQuery Sparklines in Splunk or my Splunk answer for displaying pie chart.
http://wiki.splunk.com/User_talk:Niketnilay#Topic_11:_Types_of_jQuery_Sparklines_in_Splunk_.28besides_Line_and_Bar_that_we_know_:.29.29
https://answers.splunk.com/answers/474127/pie-chart-sparkline-to-see-filling-ratio-of-splunk.html
The jQuery sparklines implementation in Splunk seem to be hardcoded for _time and _span . So pie slices are based on span and can not be changed. Since Splunk officially does not support additional sparklines like pie, boxplot or tristate etc. it would not be possible to change span to something else.
Option 1: Tweak query to prepare results for jQuery tristate sparkline
However, if you can form your Splunk query in a way that your status is a value like up=1, down=-1 and unknown=0 for each time bucket (span) (possibly using streamstats), then you can use TRISTATE sparkline .
Option 2: Use pie charts with Trellis layout to plot all host with respective status
As discussed check out Trellis Layout where you can show pie chart for count of status as up, down and unknown and split to separate panels using your asset_type.
PS: I am attaching a run-anywhere dashboard example which uses Splunk's _internal index to plot Splunk component status(log_level) as INFO(green), WARN(yellow) or ERROR(red). You can use your own query with asset_type instead of component and status as up, unknown and down instead of INFO, WARN and ERROR.
<dashboard>
<label>Trellis Pie</label>
<row>
<panel>
<chart>
<search>
<query>index="_internal" sourcetype="splunkd" log_level="*"
| stats count by log_level component
| head 20 </query>
<earliest>-24h@h</earliest>
<latest>now</latest>
</search>
<option name="height">540</option>
<option name="charting.fieldColors">{"INFO":#65a637,"ERROR":#f7bc38,"WARN":#d93f3c}</option>
<option name="charting.axisTitleX.visibility">collapsed</option>
<option name="charting.axisTitleY.visibility">collapsed</option>
<option name="charting.axisTitleY2.visibility">collapsed</option>
<option name="charting.chart">pie</option>
<option name="charting.drilldown">none</option>
<option name="charting.legend.placement">none</option>
<option name="trellis.enabled">1</option>
<option name="trellis.size">small</option>
<option name="trellis.splitBy">component</option>
</chart>
</panel>
</row>
</dashboard>
... View more