AWS .NET SimpleDB uses https

So do not be afraid. You are secure.
Declaring Type: Amazon.SimpleDB.AmazonSimpleDBConfig
Assembly: AWSSDK, Version=1.3.8.0

public AmazonSimpleDBConfig()
{
    this.serviceVersion = "2009-04-15";
    this.serviceURL = "https://sdb.amazonaws.com";
    this.userAgent = AWSSDKUtils.SDKUserAgent;
    this.signatureVersion = "2";
    this.signatureMethod = "HmacSHA256";
    this.proxyPort = -1;
    this.maxErrorRetry = 3;
    this.fUseSecureString = true;
}

Using PowerShell for common AWS SimpleDB operations

#Create SimpleDB client

Add-Type -Path "C:\AWS SDK\1.3.8.0\bin\AWSSDK.dll"
$sdb=[Amazon.AWSClientFactory]::CreateAmazonSimpleDBClient('Key Id', 'Secret Key')

#Create Domain

$req = (new-object Amazon.SimpleDB.Model.CreateDomainRequest).WithDomainName('Contacts')
$sdb.CreateDomain($req)

#List Domains

$req = (new-object Amazon.SimpleDB.Model.ListDomainsRequest)
$sdb.ListDomains($req)

#Insert Item

$req = (new-object Amazon.SimpleDB.Model.PutAttributesRequest).WithDomainName('Contacts').WithItemName('user1');
$req.Attribute.Add((new-object Amazon.SimpleDB.Model.ReplaceableAttribute).WithName('FirstName').WithValue('Konstantin'))
$req.Attribute.Add((new-object Amazon.SimpleDB.Model.ReplaceableAttribute).WithName('LastName').WithValue('Vlasenko'))
$sdb.PutAttributes($req)

#Query All Items

$req = (new-object Amazon.SimpleDB.Model.SelectRequest).WithSelectExpression('select * from Contacts')
$sdb.Select($req)

#Query Item

$req = (new-object Amazon.SimpleDB.Model.SelectRequest).WithSelectExpression('select * from Contacts where itemName()="user1"')
$sdb.Select($req)