Both "a great number" and "a lot of" are grammatically correct in this sentence. However, "a lot of" is more commonly used and sounds more natural in casual conversation. So, it would be better to say, "There is a lot of interest in wearable technology."
Both "a great number" and "a lot of" are grammatically correct in this sentence. However, "a lot of" is more commonly used and sounds more natural in casual conversation. So, it would be better to say, "There is a lot of interest in wearable technology."