I need a personal alarm system that works at my home and also when I am not at home. Suggestions?

I want only one device for that. Not with Tmobile tow. Alert1 offered service anywhere in the USA but when I got it it did not reach their call center from my home. . . . T-mobile not in my area. Well, I didn't know. I need to know which is economical and which will work at my house and when I am out and about! And, with only one pendant for both. Please tell me what will give me that. I live in Leon county Texas at postal zone 77871.