I use a Accucheck Aviva with Downloading capabilities and it is very accurate. I take a 9-10 hour fasting check each morning. Just depends on when I eat dinner. 155 is high by the ADA or the ACE standards. You need to see a doctor and have a glucose tolerance test down.
Hope all goes well.
To address your subject question, "How accurate are those home devices?", I can only comment on what I use, the Johnson & Johnsons One Touch LifeScan systems. This is what my doctor recommended and it is accurate. If you are unsure of the accuracy of your meter, you should have asked the pharmacist and you doctor on a brand they recommend prior to purchase.
Your 155 fasting reading is high. Ask your doctor for an HgbA1c test as well. You can read about it here - http://tinyurl.com/2gjspf
To start controlling your diabetes start reading other posts. It has been discussed here many times over. A good Web site is the American Diabetes Association
http://www.diabetes.org/home.jsp