Add an appointment/email/phone activity to CRM 2011 via PowerShell (REST/oDATA)

I am looking to move some older list data into CRM 2011, so I wanted a way to create some “activities” via powershell. Below is the code to do that. In the first part of the code, I create a PowerShell object and then I convert it to a JSON object via PowerShell 3’s new ConvertTo-JSON cmdlet.

$JsonObject = New-Object psobject -Property @{
ActivityTypeCode = "appointment"
Subject = "jbmurphy TEST"
Description = "This is a descritpion"
ScheduledStart = "2012-03-20T18:00:00Z"
ScheduledEnd = "2012-03-20T18:00:00Z"
Location = "Office"
}

# I am using PowerShell 3's ConvertTo-Json
$jsonEntity=$JsonObject | ConvertTo-Json
#$url="http://crmserver.company.com/OrgName/xrmservices/2011/OrganizationData.svc/EmailSet"
#$url="http://crmserver.company.com/OrgName/xrmservices/2011/OrganizationData.svc/PhoneCallSet"
$url="http://crmserver.company.com/OrgName/xrmservices/2011/OrganizationData.svc/AppointmentSet"

$http_request = New-Object -ComObject Msxml2.XMLHTTP
$http_request.open('POST', $url, $false)
$http_request.setRequestHeader("Accept", "application/json")
$http_request.setRequestHeader("Content-Type", "application/json; charset=utf-8")
$http_request.send($jsonEntity)
$http_request.statusText