"Self-Measured Blood Pressure Monitoring in the Management of Hypertension: A Systematic Review and Meta-analysis"
http://annals.org/article.aspx?articleid=1722499 
"Conclusion: Self-measured BP monitoring with or without additional support lowers BP compared with usual care, but the BP effect beyond 12 months and long-term benefits remain uncertain. Additional support enhances the BP-lowering effect."