Detect  the AP availables using the Native Wifi API library is really simple. to do this we need to use GetNetworkBssList function which is a wrapper for the function WlanGetNetworkBssList.

This source code uses the Managed Wifi API, The library uses the Native Wifi API, available since Windows Vista and Windows XP SP2 (in a limited fashion, and only after applying a hotfix provided in KB article 918997). Older versions of Windows are not supported.
Before running the code you need to download the library from this location. Build the project “ManagedWifi.csproj” and then add the reference to the source code listed below.

namespace DelphiPrismAPWifidetection;
//Author : Rodrigo Ruz. 2009-10-15
//Shine Your crazy Diamond.

interface

uses
NativeWifi,//You must add the reference to the library ManagedWifi.dll
System.Text;

type
  ConsoleApp = class
  private
    class method GetStringForSSID(ssid : Wlan.Dot11Ssid ) : string;
    class method FrequencyToChannel(freq:Longint) : Integer;
  public
    class method Main;
  end;

implementation

class method ConsoleApp.FrequencyToChannel(freq:Longint) : Integer;
var
tmpval1,tmpval2 : Longint;
begin
  tmpval1 := (freq mod 2412000) div 1000;
  tmpval2 := tmpval1 div 5;
  Result  := tmpval2 + 1;
end;

class method ConsoleApp.GetStringForSSID(ssid : Wlan.Dot11Ssid ) : string;
begin
    Result:= Encoding.ASCII.GetString( ssid.SSID, 0, Int32( ssid.SSIDLength) );
end;

class method ConsoleApp.Main;
begin
var client : WlanClient  := new WlanClient();
    for each  wlanIface in client.Interfaces  do
    begin
    Console.WriteLine( "┌---------------------------------------------------------------¬");
    Console.WriteLine( "|{0,-15}  {1,-45} |",'Interface', wlanIface.InterfaceDescription);
    Console.WriteLine( "├---------------------------------------------------------------┤");
    Console.WriteLine( "|{0,-15}  {1,-45} |",'GUID', wlanIface.InterfaceGuid);
    Console.WriteLine( "|{0,-15}  {1,-45} |",'Name', wlanIface.InterfaceName);
    Console.WriteLine( "|{0,-15}  {1,-45} |",'State', wlanIface.InterfaceState.ToString());
    Console.WriteLine( "└---------------------------------------------------------------┘");

    var BssList  : Array of  Wlan.WlanBssEntry:= wlanIface.GetNetworkBssList();
    for each  BssItem in BssList  do
    begin
    // for more info goto http://msdn.microsoft.com/en-us/library/ms706735%28VS.85%29.aspx
    Console.WriteLine( "┌---------------------------------------------------------------¬");
    Console.WriteLine( "|Network SSID          {0,-40} |", GetStringForSSID(BssItem.dot11Ssid));
    Console.WriteLine( "├---------------------------------------------------------------┤");
    Console.WriteLine( "| Channel Freq. (Khz)  {0,-40} |", BssItem.chCenterFrequency.ToString());
    Console.WriteLine( "| Channel              {0,-40} |", FrequencyToChannel(BssItem.chCenterFrequency).ToString());
    Console.WriteLine( "| Rssi (dBm)           {0,-40} |", BssItem.rssi.ToString());
    Console.WriteLine( "| LinkQuality (%)      {0,-40} |", BssItem.linkQuality.ToString());
    Console.WriteLine( "| MAC                  {0,-40} |", BitConverter.ToString(BssItem.dot11Bssid));
    Console.WriteLine( "| dot11PhyType         {0,-40} |", BssItem.dot11BssPhyType.ToString());
    Console.WriteLine( "| network type         {0,-40} |", BssItem.dot11BssType.ToString());
    Console.WriteLine( "└---------------------------------------------------------------┘");
    end;
end;

Console.ReadLine();
end;

end.