If you thought you cannot use Whatsapp without a mobile phone number then think again. You can use a home number or even a number provided by apps like Line2. You can even use a Google Voice number which can ring to the hangouts app on your PC so you can verify PIN Code Whatsapp gives you over the phone. Whatsapp can detect if you are on a tablet or not, but you can easily spoof that to make it look like you are on a Mobile device. One such app is the Market Helper which requires root but makes you appear as any android device you like, you can appear as Galaxy S3 or more.
You can download the Market Helper which is free from http://codekiem.com/2013/02/13/market-helper/ or you can go on the Playstore and download the android device spoofer app which costs $1.99
This is what I did.
I installed Whatsapp and put my home phone number as the number. It then tried sending an SMS and failed. It then gave me option to receive a call and I selected that option. The house phone rank and I listened to the Whatsapp lady give me the verification code. I put that code in Whatsapp and then Voila it was working perfectly.
Another method that also worked perfectly for me without a home phone number is to use Line2 which is free and will give you a local number in the city you are in. I think they have USA and Canada numbers. When I gave Whatsapp my Line2 number for verification and hit Call Me, I noticed that Whatsapp lady left a voicemail instead of Line2 ringing so I listened to voicemail and heard the verifiation code. After that I put it in Whatsapp and I was good to go. All without a mobile or a landline.