For pitchers, the Tom House "towel drill" is always a good indoor workout option. I also have a artificial mound that I can move from the backyard into the garage ... you can throw into a screen from a short distance, but obviously it's impossible to gauge location ... you'd just be working on mechanics.
For hitting, you can use one of those hitting 'poles', i.e., that have a solid plasic/resin ball on a fiberglass rod about five feet long. One person hits while the other holds the rod and swings the 'ball' into different parts of the strike zone, i.e., inside versus outside. If you don't have a large unobstructed interior room, you can do it in the garage.
Usually, this isn't a concern out here in CA ... but we're now in the middle of storm #2 since last Fri, with storm #3 hitting tomorrow morning. We're way past our annual average rainfall already ... and still in the middle of our storm season. Getting three major winter storms in five days is unheard of in SoCal. At least this will help replenish some of our water supplies out here.
Just heard on the radio that we've received 17 inches of rain in the last 15 days ... our annual average rainfall is 12-13 inches. There should be some great white water rafting this year ... probably the best in the past decade.