The emergencySMS service lets deaf, hard of hearing and speech-impaired people in the UK send an SMS text message to the UK 999 service where it will be passed to the police, ambulance, fire rescue, or coastguard.
Simply by sending an SMS message to 999 you can call for help and the emergency services will be able to reply to you. You can register at http://www.emergencysms.org.uk/registering_your_mobile_phone.php