When it comes to domestic events, I use WhatsApp to keep on top: A motion detector in the bird and hedgehog house, the status of the garden irrigation system, doorbell, water level in the aquarium, and much more. The tool that sends me the message is Yowsup [1], and it's easy to install:

wget https://github.com/tgalal/yowsup/archive/master.zip
unzip master.zip
cd yowsup-master/
./setup.py install

Yowsup makes the WhatsApp API believe it is running on cellphone. You need a SIM card that is not yet registered with WhatsApp for the login process. I used a free prepaid card for that purpose. "Free" here means that there is no monthly base charge or contract but only pay-per-call. Some mobile service providers have such SIM cards on offer.

I opted for a provider, put the SIM card in the phone, and activated the card; you need to determine the MCC/MNC pairing, which you can find online [2]: The mobile country code for Germany is 262, the mobile network code for my network provider, Vodafone, is 2. Nothing to stop me registering now:

yowsup-cli registration -d -E android -m 262 -n 2 -p 491521234567 -C 49 -r sms

After a few seconds, you get a text message with a registration code, say, 528-142. You need this now:

yowsup-cli registration -d -E android -p 491521234567 -C 49 -R 528-142

The output contains my login credentials in the style of Listing 1. The username is my telephone number including the country code, and the password appears in line 3. Now I can put the SIM card in a back drawer. From now on, I can send WhatsApp messages on my PC.

./yowsup-cli demos -l "491521234567:VQOHbVldOAjd+5GKIrHVWRNZkV0=" -s 491721234567 "Howdy, Post"

and receive them on my mobile phone (Figure 1). I have to go – my message just reached me: Strawberry harvest!

Figure 1: A "Hello World!" sent by Charly to the phone.