android: Determine security type of wifi networks in range (without connecting to them)

I think you can find it in the source code of Settings.apk.

First you should call wifiManager.getConfiguredNetworks() or wifiManager.getScanResults(),
then use the two methods below: (find them in AccessPoint class "com.android.settings.wifi"):

static int getSecurity(WifiConfiguration config) {
    if (config.allowedKeyManagement.get(KeyMgmt.WPA_PSK)) {
        return SECURITY_PSK;
    }
    if (config.allowedKeyManagement.get(KeyMgmt.WPA_EAP) ||
            config.allowedKeyManagement.get(KeyMgmt.IEEE8021X)) {
        return SECURITY_EAP;
    }
    return (config.wepKeys[0] != null) ? SECURITY_WEP : SECURITY_NONE;
}

static int getSecurity(ScanResult result) {
    if (result.capabilities.contains("WEP")) {
        return SECURITY_WEP;
    } else if (result.capabilities.contains("PSK")) {
        return SECURITY_PSK;
    } else if (result.capabilities.contains("EAP")) {
        return SECURITY_EAP;
    }
    return SECURITY_NONE;
}

Hope this is helpful.