I've made progress on this. Some things I've learned:
1. The phone library must be selected in the Libs tab.
2. You need the exact package name - I was getting this slightly wrong & Erel's suggestion helps here. In my example it is "rms.Alarm" - you need the quotes.
3. I was able to run this from Service_Start
Example Code:
Dim pm As PackageManager
Dim in As Intent
in.Initialize("","")
in=pm.GetApplicationIntent("rms.Alarm")
If in.IsInitialized Then
StartActivity(in)
End If
Thanks to Erel & other people's examples.