I just started doing the following and it has helped.
A lot of my parents are avid text messager senders. I'm not, but I learned that I can E-Mail my messages right to their cell phones. When I do this I usally get immediate responses and even when I don't I know they get the message because I know how much they use their phones. You get their cell numbers and providers from then and then add the tel numbers to following.
ATT or Cingular - number@cingularme.com,
number@mobile.mycingular.com,
number@txt.att.com
T-Mobile - number@tmomail.com(Update: If it doesnt work, try number@tmomail.net) Thanks lex241
Verizon - number@vtext.com
Sprint - number@messaging.sprintpcs.com (Sprint PCS)
number@messaging.nextel.com (Nextel)
Alltel - number@message.alltel.com
Virgin Mobile - number@vmobl.com
Boost - number@myboostmobile.com
I only send brief messages this way such as; "Reminder Den Meeting this Monday" or "Please check E-Mail for important message"
Hope this works out for you if you try it.