Retrieving location data from OpenPaths.cc using DevDefined.Oauth library (http://nuget.org/packages/DevDefined.OAuth). Code is based on http://www.markerstudio.com/technical/2009/09/net-oauth-sample-working-with-justintv .

OpenPathsRequest.cs

public class OpenPathsRequest
{
    private static DateTime epoch = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);

    private const string accessKey = "your personal access key";
    private const string secretKey = "your personal secret";
    private const string url = "https://openpaths.cc/api/1";
    private OAuthSession session;

    public OpenPathsRequest()
    {
        var consumerContext = new OAuthConsumerContext
        {
            ConsumerKey = accessKey,
            ConsumerSecret = secretKey,
            SignatureMethod = SignatureMethod.HmacSha1,
            UseHeaderForOAuthParameters = true
        };
        session = new OAuthSession(consumerContext, url, url, url);
    }

    private string GetWebResponseAsString(HttpWebResponse response)
    {
        Encoding enc = System.Text.Encoding.GetEncoding(1252);
        StreamReader loResponseStream = new StreamReader(response.GetResponseStream(), enc);
        return loResponseStream.ReadToEnd();
    }

    private double UtcToUnixTimestamp(DateTime utcDateTime)
    {
        var unixTimestamp = (utcDateTime - epoch).TotalSeconds;
        return unixTimestamp;
    }
        
    public string GetResponse(DateTime? utcStartTime = null, DateTime? utcEndTime = null, int numPoints = 0)
    {
        var pars = new Dictionary<string, object>();
        if (utcStartTime.HasValue)
        {
            pars.Add("start_time", (long)UtcToUnixTimestamp(utcStartTime.Value));
        }
        if (utcEndTime.HasValue)
        {
            pars.Add("end_time", (long)UtcToUnixTimestamp(utcEndTime.Value));
        }
        if (numPoints != 0)
        {
            pars.Add("num_points", numPoints);
        }
        
        // openpaths.cc requires signing before adding query parameters
        // (I believe this is not according to the oauth specs but it works)
        var request = session.Request().Get().ForUrl(url).SignWithoutToken();
        if (pars.Count > 0)
        {
            request = request.WithQueryParameters(pars);
        }
        
        var response = request.ToWebResponse();
        var result = GetWebResponseAsString(response);
        return result;
    }
}

class Program
{
    static void Main(string[] args)
    {
        var now = DateTime.UtcNow;
        var request = new OpenPathsRequest();
        var response = request.GetResponse(now.AddHours(-12), now, 5);
        Console.WriteLine(response);
        Console.WriteLine("Press any key...");
        Console.ReadKey();
    }
}