Wrote up a function this afternoon to make it quicker and easier to modify motion detection settings for a camera. Might just refactor it a little and include it in MilestonePSTools later.

Set-MotionDetection.ps1

function Set-MotionDetection {
    [CmdletBinding(SupportsShouldProcess, ConfirmImpact='High')]
    param(
        
        [Parameter(Mandatory, ValueFromPipeline)]
        [VideoOS.Platform.ConfigurationItems.Camera]
        $Camera,
        
        [Parameter()]
        [switch]
        $Enabled,

        [Parameter()]
        [switch]
        $ManualSensitivityEnabled,

        # Specifies the sensitivity on a scale of 0-300. Note the UI shows the scale as 0-100
        [Parameter()]
        [ValidateRange(0,300)]
        [int]
        $ManualSensitivity,

        [Parameter()]
        [ValidateRange(0,10000)]
        [int]
        $Threshold,

        [Parameter()]
        [switch]
        $KeyframesOnly,

        # Specifies the maximum time in milliseconds to process an image for motion detection
        [Parameter()]
        [ValidateSet(100,250,750,1000)]
        [int]
        $ProcessTime,

        [Parameter()]
        [ValidateSet('Normal', 'Optimized', 'Fast', IgnoreCase = $false)]
        [string]
        $DetectionMethod,
        
        [Parameter()]
        [switch]
        $GenerateMotionMetadata,

        [Parameter()]
        [ValidateSet('Off', 'Automatic', IgnoreCase = $false)]
        [string]
        $HardwareAccelerationMode,
        
        [Parameter()]
        [switch]
        $UseExcludeRegions,

        [Parameter()]
        [ValidateSet('Grid8X8', 'Grid16X16', 'Grid32X32', 'Grid64X64', IgnoreCase = $false)]
        [string]
        $GridSize,

        # Specifies the exclusion regions as a string of zeros and ones with a length of 64-4096 characters depending on the chosen GridSize.
        [Parameter()]
        [string]
        $ExcludeRegions
    )

    process {
        $motion = $Camera.MotionDetectionFolder.MotionDetections[0]
        $propertyNames = $motion | Get-Member -MemberType Properties | Select -ExpandProperty Name
        
        $dirty = $false
        foreach ($key in $PSCmdlet.MyInvocation.BoundParameters.Keys) {
            $Camera | Get-Member -
            if ($key -notin $propertyNames) {
                continue
            }

            $value = $PSCmdlet.MyInvocation.BoundParameters.$key
            
            if ($motion.$key -ne $value) {
                Write-Verbose "Setting $key to $value on $($Camera.Name) ($($Camera.Id))"
                $motion.$key = $PSCmdlet.MyInvocation.BoundParameters.$key
                $dirty = $true
            }
        }
        
        if ($PSCmdlet.ShouldProcess("Motion Detection Settings for $($Camera.Name) ($($Camera.Id))", "Update")) {
            if ($dirty) {
                Write-Verbose "Saving motion detection settings on $($Camera.Name) ($($Camera.Id))"
                $motion.Save()
            }
        }
        elseif ($WhatIfPreference) {
            $result = $motion.ValidateItem()
            if ($result.ValidatedOk -ne $true) {
                foreach ($validationError in $result.ErrorResults) {
                    Write-Error "Validation failed for property '$($validationError.ErrorProperty)': $($validationError.ErrorText)"
                }
                
            }
        }
    }
}