Through his foundation, billionaire philanthropist Bill Gates is taking on a range of issues in education. But in his annual letter released Wednesday, he zeroed in on one area in particular: measuring and improving teacher progress.

The big theme of the letter was innovation in measurement and the value of setting goals and finding the right metrics to track progress — not a surprising position from the man who built Microsoft.  But especially given the dearth of feedback most teachers currently receive, he said, the opportunity for teacher evaluations to improve education is particularly strong.

“I think the most critical change we can make in U.S. K-12 education is to create teacher feedback systems … that are properly funded, high quality, and trusted by teachers,” he wrote.

Since 2009, the Bill and Melinda Gates Foundation has funded the Measures of Effective Teaching (MET) project to figure out how to build an evaluation and feedback system with the goal of helping teachers improve.  After working with 3,000 classroom teachers, the project this month released itsthird and final report, maintaining that to evaluate teacher effectiveness, schools should use student surveys, teacher observations by trained evaluators and standardized test scores.

One of the MET project’s partners was  Teachscape, a company founded in the late 1990s that provides software and support for video-based teacher evaluations. Over the years, support for video-based teacher evaluations has waxed and waned.  But as video technology has improved and become more ubiquitous (in professional and personal settings) — and amid calls for teacher improvement and accountability — demand for observation tools has grown.

More teacher training programs are moving toward the use of video as a part of documenting candidate readiness for certification (not just for evaluation purposes but for self-reflection and self-improvement). And the American Association of Colleges for Teacher Education has endorsed the use of video observation in the certification process.

In the past year, a few startups have emerged to serve that need, includingSmarterCookie, which was a part of the ed tech startup accelerator Imagine K12, Edthena and Torsh. Essentially, the companies enable teachers to easily record themselves during class, upload the video to a secure platform and then share the video with coaches and mentors to receive time-stamped feedback.

Since launching Edthena, Adam Geller, the company’s co-founder and former Teach for America teacher, said it’s worked with Teach for America, the Uncommon Schools charter school organization, the University of Michigan and other organizations. Instead of focusing on teacher evaluation, he said, Edthena’s emphasis is on improvement and giving teachers a safe place for receiving feedback from the best mentors and coaches, wherever they are.

“It replicates the experience of having someone sit at the back of the classroom, but it takes away time and geographic barriers,” he said.

Teachboost, another startup backed by Imagine K12, takes a different approach to teacher development by providing a mobile-optimized (and web-based) tool for gathering and analyzing teacher feedback. Schools can use the product to streamline teacher evaluations and observations but teachers can also use it to solicit feedback from peers and share their progress.

When it comes to teacher feedback, as with any area in education, innovation isn’t just about the technology. As Gates suggests in his letter, teachers need to trust the system, be willing to commit their time and feel confident that it will provide specific enough feedback to help them actually improve and progress professionally. Technology can only play a bit part in much of that, but it can still play an important role in helping to deliver more personalized and contextualized support for teachers.