"Knowing which numbers are capable of receiving SMS and which aren't has some value."

This isn't difficult - I wrote a shell script named "lookup" that will give me background info for any phone number I feed it and tell me what kind of number it is, what carrier it is, who it belongs to, etc.:

  # lookup 415-333-2222

  {"caller_name": {"caller_name": "WIRELESS CALLER", "caller_type": null, "error_code": null}, "country_code": "US", "phone_number": "+14153332222", "national_format": "(415) 333-2222", "carrier": {"mobile_country_code": "311", "mobile_network_code": "489", "name": "Verizon Wireless", "type": "mobile", "error_code": null}, "add_ons": null, "url": "https://lookups.twilio.com/v1/PhoneNumbers/+14153332222?Type=carrier&Type=caller-name"}

... which is very useful since I often send (personal) SMS from the command line and sometimes I need to know if a number can receive it ...

I'm not going to paste the entire script here but the meat of it is:

  /usr/local/bin/curl -X GET "https://lookups.twilio.com/v1/PhoneNumbers/$number?Type=carrier&Type=caller-name" -u $accountsid:$authtoken

... and each lookup costs a penny or a half a penny or something ... I forget ...