Apple apparently has a growing wishlist of health features for future versions of the Apple Watch, some feasible and some far-fetched. According to a Wall Street Journal report, Apple’s plans include various types of monitoring, including blood pressure, temperature, sleep, and blood sugar. The details come just after reports that the release of the next Apple Watch is likely to be delayed because of manufacturing issues.

Some of the planned features outlined by the WSJ involve adding new sensors to the Watch. Apple wants to develop a sensor that can act as a proxy for a blood pressure cuff without squeezing the wrist. Blood pressure measurement has been in Apple’s plans for years; the company filed a patent application in 2016 for a wearable blood pressure monitor.

Apple’s competitors are also interested in blood pressure tracking. Samsung’s Galaxy Watch was approved to track changes in blood pressure in South Korea last year. There’s been debate around the accuracy and usefulness of the feature, and it has to be calibrated with measurements from conventional blood pressure cuffs every four weeks.

Apple had plans to add a temperature sensor to this year’s Watch, according to earlier reports from Bloomberg, but the addition appears to have been pushed to next year. The first slated use for temperature sensing, according to the WSJ, might involve fertility tracking, with hopes that it could eventually detect fevers.

Other wearables, like Amazon’s Halo Band and Fitbit’s Sense, have sensors for skin temperature, though that measurement is different from the internal body temperature read by a thermometer. Earlier this year, the Food and Drug Administration cleared digital birth control Natural Cycles to use temperature data from wearables like the Oura smart ring.

Apple also wants to expand the Watch’s sleep and blood oxygen tracking abilities, says the WSJ, to someday be able to detect sleep apnea, a disorder that causes people to stop breathing during sleep. Sleep disorders are complicated, and diagnostic sleep studies involve multiple kinds of monitoring through the night. For that feature to work, Apple would probably have to figure out the best times to take blood oxygen readings — keeping the sensor on all night would drain the battery pretty quickly.

Apple reportedly also plans to seek FDA clearance for existing Watch features, like heart rhythm tracking for people with irregular heart rhythms and alerts for drops in blood oxygen levels. The current FDA clearance for the Watch’s EKG feature doesn’t include use by people who have a diagnosed heart rhythm condition like atrial fibrillation, and the Watch’s blood oxygen monitor isn’t cleared as a medical device.

One of the furthest-out features that Apple is continuing to study, according to the WSJ, is blood sugar tracking and diabetes detection. Apple has been trying to develop noninvasive glucose monitoring for years and reportedly hasn’t had much success.

The anonymous sources cited by the WSJ caution that many of the features being considered “might never be rolled out to consumers.” Health tech advancements, and regulatory approval for them, take years of development and testing. As much as companies want to add a slew of health features to wearables — and even as wearables are more commonly used in medical research — they’re still not advanced enough to replace conventional diagnostic tools.