A mobile phone can have only one phone number, right?
Wrong. Apps such as Burner and Google Voice can give you a second number, after a fashion. The newest option: Pinger's Sideline, a business-oriented app that supplies a free second number for your Android phone or iPhone.
The idea here is that your smartphone is your personal phone, and you wouldn't necessarily want to use that as your business phone. That's why you still see some folks carrying around two phones, a monumental hassle to say the least.
Sideline is a breeze to set up, and along the way you get to choose from an assortment of available numbers in your current area code.
Once you've completed the process, the app works more or less like your stock phone app, allowing you to place calls and send texts with a few taps. However, your entire call/message history is presented in one long list, without a search option -- so that's not exactly ideal.
You'll also have to contend with fairly chunky banner ads, omnipresent at the bottom of the screen. That's the price for this otherwise free app and service, but in exchange you get phone service that's exactly that: Calls and texts are routed over your carrier's voice and SMS networks, using your existing plan. (Obviously this is best if your plan has unlimited minutes and messages.) In other words, this isn't a data-powered voice-over-IP service, meaning call quality will be exactly as good as it is when you make or take a call using your regular number.
And, sure enough, in my brief testing of Sideline, it worked exactly as advertised. Callers sounded great, and incoming calls were indistinguishable from regular calls -- except for the "Sideline" caller ID prefix that appeared, which is how you know it's a call to your "business" number. The service also lets you create a custom voicemail greeting.
If there's a catch at all, it's that your new number gets deactivated after 30 days of inactivity. (You can pay $0.99 per month for a Pro version that lets you keep it indefinitely.) You'll also hear a snippet of advertising when you place an outgoing call, but it's short and merely takes the place of the ringing you'd normally hear.
Update: That advertising snippet was not generated by Sideline, but rather by RingPlus, the carrier for the phone I was testing. According to a Sideline rep, there are no audio ads associated with the app.
Although the Sideline app is fairly rudimentary, the service is solid -- and potentially invaluable for anyone seeking a second phone number.