A recent addition to conventional foiling is dieless foiling. This is also known as Cold Foiling, but it must be noted that dieless foiling can use heat to transfer the foil.
The most successful and suitable markets have been the label industry, Reel to reel tubes manufacturing, and fabrics. This has brought printing and foiling much closer together as regards technology and costs.

The basic principle is the applying of adhesive to the substrate prior to the foil being applied. The advantages being : 
1) Running speed
2) No die cost.
3) Very fine detail and screens possible.
4) Ease of set up.
5) Small capital equipment cost.
6) Easy conversion to inline foiling.

To date the most successful method of printing the adhesive is flexo, although silk screen and letterpress are possible. Other printing methods are under review.
 

Cold Dieless Foiling
 

Free Radical : This is the most recent process addition, and has to date proven much easier than its counterpart below. The main difference is that the adhesive is applied and, prior to any curing, the foil is applied through a nip roller. Then, while the foil carrier is still on the substrate, both are passed through a UV lamp to allow full curing together. This works due to a critical thickness of  Finally the foil carrier is separated to leave the foil on the fully cured adhesive. This has improved the results, gloss level and ease of set up. The critical semi cure process (below) is no longer needed, and this is a much easier system to control.

Cationic : This method was the first to be introduced and uses UV lamps to semi cure the adhesive, after which the foil is applied through a nip roller and then separated from the substrate. Finally the "foiled" adhesive is fully cures as it moves to the material rewind.
The initial semi cure is critical, and can be difficult to get right.

Hot Dieless

 This method uses existing hot foil machines or stations, but uses a smooth cylinder instead of a die. The adhesive is applied using one of the print stations, fully cured and then passed under the hot foil head. The foil is separated by the normal rewind unit and the process is complete. This method is yet to be perfected for labels but is fully proven for reel to reel tube manufacturing. 
The difficulty with labels and other graphic applications, is that the foil head needs to be dedicated to dieless foiling to avoid surface wear from partial image dies. This can cause "missing" of the foil.
The adhesives have also been problematic in running and curing properly.