New research from the Nielsen Company’s has revealed the extent to which tablets and smartphones have become complementary devices for TV viewing plus the continued surge in online video use.

According to Nielsen’s recent survey of nearly 12,000 connected device owners, 70% of tablet owners and 68% of smartphone owners said they use their devices while watching television.

Digging deeper, tablet owners said 30% of their time spent with their device was while in front of the TV compared to 21% who were lying in bed. By contrast, smartphone owners say that a fifth of the time they use their smartphones is while watching TV, compared to 11%.

On a separate note, further research from Nielsen found that during April 2011, Americans streamed 14.7 billion videos, the most streams ever in a month. Yet even though the number of videos streamed increased, total viewing time actually decreased during the period. There were 141.4 million unique U.S. video viewers who spent an average of 4 hours, 31 minutes viewing video over the course of the month.

The top video sites were YouTube, VEVO, Facebook, Yahoo!, MSN/WindowsLive/Bing, AOL Media Network, The CollegeHumor Network, Hulu, CNN Digital Network, and Fox Interactive Media. YouTube’s usage was at an all-time high in April as their viewers consumed 8.7 billion streams, up 7 percent from last month. In terms of average time spent per user on a site, Tudou lead Hulu.