We tried Magic Jack, too. It didn't work for us, either. The only computer it would work on was my laptop, which tethered me to our phone system (base station had to be connected to the MJ in order for all the phones in the house to work). Drove me crazy because I have a laptop for a reason! Also, call quality drove OTHERS crazy. It worked fine on our end, but our elderly relatives and some local friends could really tell the quality difference and in the case of the elderly relatives they simply could not carry on a conversation any longer than 3 minutes.
We purchased an Ooma from Costco and LOVE it!!!! It was under $200 out the door and we could have returned it easily, if it didn't work out. It has worked out wonderfully for two or three years coming up in early December. (We were just discussing it and cannot recall which year we got it. It seems like we've always had it.) Our cell phones don't always work in our house and we want the family house phone. I had already dropped all "extras" on the landline phone service and had gotten the bill down to the bare bones, which was costing us just under $23/month. Now we have a $0 phone bill for our home phone...no bill at all. The Ooma paid for itself in about 8 months of no longer having a phone bill and we enjoy it and use it ever since for free.
It does not need a computer to work, but it does require an internet connection. When the power goes out, the Ooma goes out (as do all of our computer peripherals). We had a major blackout back in September and the whole county was without power for about 12 hours (starting in the afternoon). The cell phones had power (they were already charged), but still did not work due to the congested lines. Folks with regular landline phones could not get calls to go through, either, due to congested lines. This was an extreme situation, but that's how it went down.
Under regular conditions, if you keep a regular telephone (non-cordless) you can plug it into the regular wall jack and make an emergency call. At least here in our service area and other areas where my friends have also tried it.
For awhile, one could not make 9-1-1 calls from any of these "alternative" phones. Magic Jack could not when we had it. The Ooma did then and still does now. You must follow the online instructions for set-up when you get it, though. There are ways to use the Ooma without setting it up properly, too, and it would NOT allow 9-1-1 calls when done that way.
The other challenge with any "alternative" phones (even cell phones) is the reverse 911 system only has landline phone number automatically included in our county. It was easy to add our mobile and Ooma numbers to the system online.