Questions that ask the user to select from a range of values using a slider have been included in odkCollect and are now also available in fieldTask.
Support for these question types has just been added to Smap Server version 17.08.03 which will be deployed onto hosted servers next Saturday or earlier.
Add a range question to your survey using the online editor. You then have to specify 3 parameters in the parameters property.
start=1 end=5 step=1
start=-2.0 end=2.0 step=0.5
If you add a decimal point to any of your parameters then the collected data will also be decimal. Otherwise it will be integer.
The Survey Edit Reference document has been updated to include range. Range questions are not supported in the xlsForm editor yet.