Downloading Wget is not necessary; the .NET Framework has web client classes built in.
$wc = New-Object system.Net.WebClient;
$sms = Read-Host "Enter SMS text";
$sms = [System.Web.HttpUtility]::UrlEncode($sms);
$smsResult = $wc.downloadString("http://smsserver/SNSManager/msgSend.jsp?uid&to=smartsms:*+001XXXXXX&msg=$sms&encoding=windows-1255")