Allows people to subscribe to SMS text message updates of your web site to users via cell phone.
No. (123) 456-7890 is the same as 123-456-7890 is the same as 1234567890 is the same as 123 456 7890 ad infinitum
No, you can manually add subscribers phone numbers from the plugin settings page, or you can use the shortcode to place the signup form on any page or post of your WordPress website.
You can either manually send out SMS text updates at your discretion, or click the checkbox on the plugin settings pages to send out a text message update each time a new post is published. You can even add page ID's to notify subscribers of specific page updates.
You have to remember that this plugins sends out emails to email to SMS gateways for cell phone providers (which are "secondary" priority). We have personally not had a problem with text messages going out, but we always know that email to SMS texts are not guaranteed to be delivered. We also know that different webhosts and different servers may have different results - espesically if you're sending out a lot of SMS text messages. If a provider thinks you're sending too many (or somebody flags your IP as spam) some people may not receive your text messages (your mileage may vary).