Can I send an iMessage to a iPad user from my iPhone?
How does an iPhone send iMessages to iPad:


Make sure iMessage is set "on" on both devices
On your iPhone, go to Contacts and find your friend's name to check whether or not you have his email address. If not, you need to add his email address.
On the iPad, go to settings>>messages>>recieve at>>add email. Put your friend's email address from step 2. It will say "verify".
Your friend need to verify by checking his email. There'll be an email from Apple. Open the email and he'll be asked to click on the verify link. Click on it and he'll be directed to Apple's homepage. Just follow the instructions there.
Once your friend has verified his email address, the word "verify" in step 3 disappears. Now you can iMessage him.
On your iPhone, go to contacts and choose your friend's name. Click on "send message" and choose the email address that was just verified. You're now directed to the message screen.
In the "To" field, you 'll see that the email adress is missing "@". Ignore it.
Make sure that the send button is blue. Now just type your message and send.


Hope this works!