One morning in September, I logged on to the website of HelloMD, a medical start-up that promises to connect patients with doctors instantly over the Internet. I filled out my personal details, explained my ailment — I often get heartburn — and entered in my credit card number to cover the $50 consultation fee.

Within 10 minutes, a pediatrician based near Washington who is licensed to practice medicine in my home state of California popped up on my screen. She appeared to be sitting in her home — there were a few teddy bears and ceramic figurines on a cabinet behind her — and she wore a red shirt, not a white coat.

The doctor asked about my medical history, current symptoms and familiarity with certain medicines. The interview lasted about three minutes, after which she announced what everyone who visits HelloMD expects to hear: According to her diagnosis, my heartburn made me a candidate for medical marijuana, which has been legal in California since 1996.

HelloMD is at the forefront of a new trend in Silicon Valley: the cannabis tech start-up. As marijuana laws are being loosened across the country, entrepreneurs and investors are creating new businesses to cash in on what they see as an emerging bonanza. Like start-ups in other industries, these firms are trying to use technology to bring speed and efficiency to what has long been a face-to-face, pen-and-paper market. In the process, they are also trying to alter mainstream perceptions of the marijuana industry, shedding the ganja and Rasta imagery to cultivate a wider audience.