Hello to everyone!!
Starting from one existing project (http://hacknmod.com/hack/arduino-based-snail-mail-alert-for-your-smartphone/), I set up a new project of snail mail alert using an Arduino.
When a snail mail arrives, the Arduino sends a notification via Twitter or simply opens an external web page (which can send me an email or notify me via chat, for example).
It's similar to the original application, but my project also allow you to configure the behaviour of your Arduino by editing a text file on the SD card, and it's not limited to a push notification for iPhones.
Here is the sample of the configuration file:
# Begin of configuration file
# Comment (starting with # character) and newlines are skipped
# Network configuration
MAC=00:22:17:0D:70:80
# IP like 192.168.1.1 or IP=DHCP
IP=DHCP
# or IP=192.168.1.250 or similar...
# Notification type: TWITTER | WEB
NTYPE=TWITTER
# Twitter notification configuration
# Get an authentication ID from this website: http://arduino-tweet.appspot.com/
TWITAUTHID="YOUR_TWITTER_AUTH_ID"
TWITMSG="New Snail Mail arrived"
# Web notification configuration (http://... with final slash '/' for directories)
WEBURL="http://192.168.1.235/web/testarduino.php"
#WEBURL="http://www.mydomain.com/arduino/"
The sketch uses the following libraries: SD, Ethernet, EthernetDHCP, EthernetDNS, Twitter.
Its size is 28550 bytes, so it can run on an Arduino One.
The sketch automatically solve the DNS domain, if it's not an IP address.
Here is the scheme:
The led resistor is 150 Ohm and the button one is a 4.7K or 10K Ohm.
You can use for example a tilt sensor instead of the button.
I attach the sources of the project, hoping everyone could be interested 
If someone is interested, I can post a video of the working project.
Bye!!
snailmailalert_final.zip (9.14 KB)