Cost effective and state of the art may be mutually exclusive.
A state of the art system may use a program like Expedition. It has current data built-in. You input your boat's polars and download grib files. Expedition will provide you with a chart of the course to steer as well as a table with the course to steer and target boat speeds in regular intervals. The grib files come from SailDocs via email.
One user has developed a couple of add-ons that provide tables which indicate whether or not your are sailing to the target speeds.
I think Expedition runs about $1300.
ISPA Yachtmaster Offshore Instructor Evaluator
CYA Advanced Cruising Instructor
IYT Yachtmaster Coastal Instructor
As I sail, I praise God, and care not. (Luke Foxe)