I don't have a receiver yet, so I can't say I've actually used it, but I did manage to load the WiDi software onto my XPS 12. I loaded the Intel Generic HD 4000 drivers, rather than the Dell specific ones (which requires a reboot). In typical Intel fashion, they make it hard-ish to find, but here is the current link:
https://downloadcenter.intel.com/Detail_Desc.aspx?agr=Y&DwnldID=22842&lang=eng
I don't know if it helped or not, but I also installed Intel WiDi Media Share setup, found at:
https://downloadcenter.intel.com/Detail_Desc.aspx?ProductID=3227&DwnldID=23022&lang=eng&iid=dc_rss
Then I installed the application from the beginning of this thread, and it successfully completed the installation. The WiDi dashboard launches and performs a scan, but as I said...I don't have a receiver yet, so I can't swear the whole process hasn't been for naught. I'll figure that out when I get one, I guess.